Would this be too many presents for a group of family-friend kids I know? Its their birthday?

No you haven't bought them too much :) The gifts sound fabulous, I know many little boys who love making jewelry with their sisters, as you say he joins in. It's great that you're bought them "activity" gifts that will keep them occupied and interested, I know kids love stuff like you have bought. So thoughtful of you to take a cerole too in order to ease her burden......definitely a family who has a great, caring friend.