I'm pretty sure you can't "bank" qualified expenses for later. Closest you can come is to take the money out, then put it back in to step-up basis. I don't know if you could then pay for college with loans. Maybe it depends on whether or not they're subsidized? I bet a personal loan would be fine, but then you'd pay a higher rate. Sorry I don't know the answer on that.
My bias would be to greedily use the opportunities for qualified withdrawals as they present themselves. So I'd drain the accounts in preference to taking loans. It's much better for the case where she joins a cult or becomes a SAHM or whatever after her first year of qualified expenses. Not terribly likely, but it's not clear how splitting the load optimizes for anything. I suppose using the qualified expenses to withdraw aggressively also reduces total education loan interest paid, by deferring/back-loading loans.