I think this would be fun! I have a 7 year old boy who likes to help me with my crafts. he's even learning to sew much to my DH's dismay, but he lets us do our thing
I think we could handle clothing for sure, and even for younger swappers, something as simple as letting them help pick out the design to put on an iron-on trasfer is still considered participation in my book. also the craft kit is a great idea. and maybe a little letter and a photo of the kiddo swapper if you're comfortable. my son writes letters to a cousin cross country and LOVES to send him photos of obscure things (i think) or rocks he likes or what have you. strange to me but the cousins sure seem to love getting their "buddy mail"
i think its an awesome idea and i would totally be down!