Colors for large family

I have a large extended family who wants a portrait done. They seem to be stuck on each nuclear family wearing the same color. I've had large groups wear all white, but I'm not sure what to recommend to this family. Perhaps I will tell them to wear whatever they want and to avoid fine patterns. However, they seem set on each family wearing a particular color... They want this done in the fall when the leaves are changing.

Any input would be appreciated. I think there will be around 12-14 people in the group.

I've seen photos like that and it can be a nice effect (for larger groups than you're talking about) but if taken too far it looks like everyone is in uniform. For a small group I think I would emphasize that they not wear identical clothing but rather just similarly colored clothing.

I like the idea of each family wearing similar colors. For fall, I like rich purples, burgundy, teals and browns. As long as they're not all in exactly the same shirts, I think it would look nice.