If your child is a bit bigger then they might need a larger desk to fit their size. They're also probably too big to fit in their crib at this point as well. This DIY project is a great way to turn that old crib into a full-size desk. All this person did was remove one side of the crib and apply some chalk paint to the bottom to create a play area.
It's also pretty easy to hang toys and other household items from the side of the crib after you finish everything. You just might want to be careful the kids don't get on top of it and start jumping around, but that's the case with just about any piece of furniture.