I've seen kids do a simple version of "Maahi Ve" (KHNH).
Yea, would second this one for grade-school kids.
Actually lots of the family-movie SRK songs have dance-able steps for youngsters, I think. (Like K3G with Kajol, etc)
Wedding songs often have fun and easy steps too, because everyone participates from grandmothers to toddlers and all the aunts and uncles too.