First, how many items do you aim to have for each kid to open? We have gifts from Santa and from us, and I think I had like 8-ish last year each.
Second, what do your families do about buying for kids? We always bought for all the nieces and nephews, but one of my brothers doesn't have any kids and now would have to buy for my three (soon to be four) plus other bro's 2. That seems crazy. On DH's side, we just went last year to buying for godchildren only. They still get gifts from Grandma & Grandpa.