Can our wedding return coach leave before the reception ends?

The transport quote came back with a 9:45 p.m. return departure. Our reception finishes at 11:30. We'd already told guests staying at the hotel that return transport would be provided.

Forty guests are expected on the outward coach. The operator has quoted another $260 for an additional 11:30 return run. My partner thinks people who want to stay late can arrange something themselves; I think "return transport provided" sounded like a way home after the party.

Some relatives have said they'd welcome an earlier finish, so the 9:45 coach would be useful. We haven't asked how many others would want the later run, or what other transport they could actually book.

Do we pay for both departures, shorten the reception, or explain now that the included return is early? I'm reluctant to make "you can always get a taxi" the plan when nobody has checked that part.