An easy one is to pick up 1/4" strips of red oak from Home Depot or Lowes. They come in 48" strips up to 2.5" wide but the 1.5" wide pieces are my choice. Draw a basic pyramid shape, glue on a handle block, some nock supports & tiller by thinning the width rather than the belly. Back it with paper, burlap, silk or anything simple. Makes a great kids bow. At age 6, they just need to fling some arrows for fun. If you want some dimensions, I'll go back & measure them for you. I think they came out to about 15-20# at about 22" or so. I never put one on the scale so that's just a guess. At 48", they'll hit a hard wall at about that 22" draw mark.
The only issue with these bows is they can quickly start to twist when side tillering. Scrape too much off of one side & you'll see it twist up fast. You also have to be careful not to scrape the belly when working on the handle transition area. It's easy to go a little too far & gouge the belly. A little bit is fine. Just have to be careful.
For my oldest, I also did a paper-backed red oak board bow that was 1.5" wide x 48" long and pyramid shape. This was off a shorter section of 1x2 that I had laying around. That thing did pretty well, coming in at around 25# @ 20". Of course, then he left it strung up outside in the rain one night...
None of these will win any awards but at their age, who cares? If they shoot them out in a couple years, I'll gladly make them another. They build fast.