Hivemind, activate!

I'm planning/hosting a group trip for which I'll be needing to collect scheduled payments from several friends over the course of a few months. Paypal is the obvious solution, but my problems with it are two-fold: (1) that they take a percentage chunk that will require me to overcharge my friends for an already pricy shindig, and (2) that there's no way to separate the vacation funds from my funds without establishing a brand new bank account.

It'll go down something like this. I'll post messages announcing "The hotel deposit is due two weeks. Send $200!" at which point, a dozen or so payments will filter in one by one. Once I have everyone's share, I'll immediately make the payment to hotel or the airline or the etcetera etcetera, but I just want to be really, really careful that none of that money gets swept up in any of my (sometimes automatic deduction) bill paying in the interim. All in all, the total trip cost for our full head count is going to be around $24k, and I want to be careful with that kind of money.

Any ideas?