In my state 529 there is a small annual maintence fee, but I can't bring myself to pay it for 18 years just for funzies, so we keep both girls' college dollars together. We will have to change the beneficiary at some point to catch child #2. But our plan right now is to give them even amounts of whatever we can acquire.
Honestly, I've told them that I'm open to that being a business start or a duplex downpayment or some other passion/career investment. There are many paths. If neither opt for college I guess we'll pay the tax to get it out, but I'll be a bit surprised if neither goes to college, as their dad is a professor.