Events shouldn't carry any data in my opinion, except parameterized data. In the context of a booking, for example, it would be SeatBooked {41A} instead of 41ABooked, though the latter is a better event, but harder to program for. The entire flow might looked like this:

SeatTimeLimitedReserved {41A, 15m}

SeatAssignedTo {UserA}

SeatBooked {41A}

If a consumer needs more data, there should be a new event.