Did not see that there was going to be more than one person...
And I rarely carry cash so I like to be able to tip on the card. Although I agree it's backwards. Yet, since some people says 'TIPS' stands for "To Insure Proper Service" the only way one can insure proper service would be to tip ahead of time, no?...a tip at the end won't insure you proper service next time. Unless you are definitely going with the same establishment and get the same person serving you AND they remember you tip well.
Course, you can take back a tip in this case...or maybe you can.
Again...long story short...I rarely carry cash if I can help it.