You could always do it like swap-bot where everyone gets a randomly assigned partner and everyone knows to make a set number of cards for a set person like a 2 for 2 swap ect. Then they get the address and send themselves.
Or like each person is assigned 3 or 4 partners randomly and then makes the cards for those people, that the arena does for the christmas card swap. Once again the artist sends out to the people they are assigned.
That or you could do large scale swaps where everyone makes a card for each person in the swap and they ship them out themselves.
Just suggestions! If you end up discontinuing personalized cards I might start hosting atc swaps as well and doing the whole partner assigning thing if thats ok with you!
It seems easier than everyone sending them to you and then you having to sort them out and figure out who gets what. Then you wouldn't have to worry about sending someone their own cards, someone getting the same cards from someone else, and people maxing out on getting cards made for them.
I know I personally love getting personalized cards or at least 1 card from each participant but I also know thats not always possible so I totally understand. I don't want to step on any toes or have you think I'm undermining you in any way so I hope this doesn't come across wrong!