In my experience, the best type of stand setup depends entirely on the terrain, and what the child is comfortable with. If your bait is down low in a wash with ridges surrounding it, then a ground blind on a close ridge might be good. If it's level between your stand location to the bait, then a tree stand might be better.
The first hunt I ever guided for bears was a baited hunt with a father/daughter. Daughter was 14 yrs old, and deathly afraid of heights. She was not getting in a tree under any circumstances. I brought a Double Bull blind, and she shot a really nice cinnamon boar 2 days into the hunt.
Point is, you'll know more about your child's preferences and strengths/ weaknesses than anyone. Pick a good spot, enjoy the time with your child, and make it fun and memorable for them. Peanut M&M's and hot chocolate make sitting baits much better for kids.....but Fun Size candy bars won't hurt either.