Collect money for an anniversary party

Your parents have been married half a century this year. You want to hold a party for friends and family down at the hotel in the ballroom where they met back in high school. When you see the cost of renting the place, you're a bit floored, but figure you can get enough people to contribute that it'll be possible. But with everyone all over the country, getting in touch over the phone and waiting for money to arrive by mail is taking too long. You need a faster solution you can use to contact everybody and once, get that list of guests and collect the money you need.