Whats the best way to Travel from Bucharest to Sunny Beach, Bulgaria?

We are family of 4, flying to Banaesa Airport, Bucharest. Need to get to Sunny Beach, Bulgaria. I'm fine with driving but hiring a car proving a little difficult because many hire companies do not allow you to cross the Romanian/Bulgarian border. We travel out on 23rd May 2009 for 1 week. Does anyone have knowledge of trains, buses. I've heard it could be good to catch a train from Bucharest to Rousse, Bulgaria and then catch a bus or hire a car for the rest of the journey.

Get ureself a magic carpet its defiantly quickest & best way