We did it a few years ago, although we didn't book the regular trip you see advertised all around Sunny beach, but booked the bus ticket ourselves from Bourgas and booked our own accomodation and stayed 3 nights.
Going and staying for one night is too much in my opinion, its a LONG trip stuck in a coach you really should try and stay for longer than one night, there is loads to see and do.
The trip is probably not recommended for really young children or those with a weak bladder
as we only stopped a few times and its a long journey!
Paddy