Total Cost - $50-$100, depending on what deals you find.
Fun - 9
Fun - 9
Learning - 9(very good early on for building motor skills)
If you frequent home depot, or Costco, or Wal-mart, or any other major department store, I'm sure you've seen "Kits" for building your children a play house. Generally these kits cost between $1000-$2000, and you STILL have to build the thing yourself. So I decided to just build my children something simple, for much cheaper, that they still love to hang out in. Also, since you're making it yourself, you can fit it to your own dimensions.
This is what I made - the photo's aren't too good since I've taken it back apart(because we're moving), but you get the idea. I haven't had anyone get hurt on it, and this is with having a 1 and 2 year old play on it for more than a year. I've learned a few ways to improve on it as well since putting it together.
A basic power saw.
Total Materials -
2 4x8 sheet
A box of 3" square head drive screws
A box of 2" square head drive screws
Some Carpet remnants
Either some carpet glue, or heavy duty staples with a stapler
Outside walls vary based on how you want it
First, Measure the height of your room, and the height of your kids.
Basically, go to home depot or something similar, and buy 2 4x8 Subfloor pressboard subfloor pieces. It's easiest to get one cut into 2 4x4 pieces, since you'll have to anyway, and it's easier to transport. The other, get cut into 2 2x4 pieces and 1 4x4 piece. Then, buy 4 4x4x8s, whatever material is cheapest - it'll be more than sturdy enough regardless. Mine has a 4x6 simply because I had it left over.
Have all 4 4x4s cut. Where you cut them will depend on the height of your kids and the height of your ceiling. You will have each one cut twice, into 2 large and 1 small piece you'll get rid of. You want the large cuts to be at least a few inches longer than the height of your tallest kid, and the total of the two to be a few inches shorter than the height of your ceiling. Home depot I know at least does 2 free cuts per board, by the way.
So, lets say your tallest kid is 42 inches tall and your ceiling is 8 feet, you'd cut the 2 large pieces to be 46 inches long each. Since the 4ftx4ft pieces are 3/4 inches thick each, that leaves 2.5 inches of clearance from your ceiling. This is ideal, since you don't want them climbing over the top of it.
Lastly, get something to make it softer, find the cheapest carpet remnant you can in the flooring section, you only have to cover a fairly small area, so it will probably be the smallest one there.
Now, lay 1 4x4 piece out on the floor and attach the carpet however you are going to. If you use staples, make sure they are in there deep, hammer em in after stapling if need be. Next, lay out 2 of your 4x4 boards on the floor, and set the 4ftx4ft subfloor piece on it's side. Attach the boards at the corners using around 5 of the 3" screws. Flip it over and do the same thing with the other 2 boards. After it's done, you should have the 4ftx4ft subloor piece laying flat, with 4x4s sticking up from each corner.
Lay the other 4ftx4ft on top. Once again screw around 5 screws into each 4x4. Attach carpet on top of that. You now have an open box. If need be, you can take a break and continue the next day, it's safe enough for the kids to be around it at this stage, as long as someone is in the room watching them.
Anyway, onto the next part, the ramp. This house should be placed ramp-side flat against a wall, so that they won't be able to fall off the side of the ramp. Take 2 of the 2x4s, and lay them on the ground parallel approx 2 feet apart. Then take 2 of the cut pieces of the second 4ftx8ft, and basically form a "Bridge" laying them on top of the 2x4s. The 2x4s should be out to the edges for the most amount of stability. To get an idea what I'm talking about, just look at the left side of the pictures, that is the "ramp" which you are building. Drive in a 3" screw roughly every 2 feet or so.
Next, take the remaining 4ftx4ft piece, and attach it to whatever side of the "Box" you built before that's going to be facing towards the wall. This is where you will attach your ramp to. Put the ramp up next to that newly-made "wall" of the box, to where the ramp touches the top-left corner, sort of like in the picture. Then, place around 8-10 of the 2" square drive screws through the 2x4 on the bottom of the ramp and into the newly made wall.
You should have one remaining 2x4, which you're going to use to support the other side of the ramp. Simply measure how high off the ground the top of the ramp is and cut a 2x4 piece to attach to the other side of the ramp. Be sure to attach it on the INSIDE of the 2x4, so that the ramp can go flush up against the wall. Then cut another piece to attach to the middle. This ramp won't just hold your children - it will hold your own weight in case you need to climb up after them. At around 285 lbs, it held my weight just fine. After you're done with the ramp, attach a piece of carpet to it to make it softer, and you can then push the whole thing up against a wall.
Now, take the remaining 4x4s and attach them to the top floor of the "house". Put them just inside of where the other 4x4x come up from the bottom so that you can easily screw into it from below. Once again, 5 of the 3" screws per 4x4, to make sure it's nice and sturdy. If you want, you can even drill a few holes and put a few lag bolts in there for extra strength.
Now for the last part, the "Walls" of the top floor of the house. These can be pretty much anything, depending on what you want to spend and how the room is laid out. Again, refer to the pictures for an example, I used some scrap 1x4 boards I got at home depot for the lower part of the wall, so my kids could sit there and watch TV from that angle, and I used some peg board on another wall so they could have fun looking out the tiny holes. If you use something like peg board though, make sure to reinforce it with either a 1x4 or 2x4 going across it.
For the ramp-side of the house, you can either leave it open if your toddlers are in the older range, or put a 2x4 across the top, then one more going down the middle, and block off the side that's a further drop to the ramp with a pegboard or other thin piece that you typically find located near the pegboard in the store. For mine, I had an extra 4x4 piece, so I used that.
You can paint the finished result, or leave it as-is. Either way, your kids will enjoy it easily enough to be worth the $50 or so you put into it. And I like building things, so this was a fun project for me. The reason you used square-head screws on the entire thing was, when you do want to take it apart, it'll be pretty easy as the screws won't have gotten stripped putting it in.