Thanks for the comments. Since people are coming from all over Europe (to either London or Cape Town), phone calls are less than ideal (though not impossible).
The idea would be to remove the credit card number from the database immediately upon retrieval, not store it. I suppose I could betray people's trust, but I could do that with a phone call, a pen, and a piece of paper, too. Nobody pays cash for the villa, so at some point, they have to trust that I will charge them only for their rental and then destroy any record I have of their credit card number.
Of course, it doesn't have to be a database. I just want a way for people to "pay" through the website. The transaction would happen very quickly, though not immediately, as you mention. So I'll be sure to mention that (of course, most transactions I make with my credit card take a day to appear anyway).
So: these shopping cart programs: how do they work for taking credit card information? Are they hooked in to a seller's credit card system? Is it all automatic, invisible to the buyer and seller?
Thanks,
Pat