I think it may be too late, but in the future, you may want to look into doing an air deviation. You can pick the flights, times, airline, etc. There is a charge for this, usually anywhere from $35-$50. If at all possible you can try to fly down a day early too, just to make sure you have some time to explore before the cruise.
As for the dinning arrangements, if you all booked together and requested the same time, hopefully you will be seated together, if not just see the Madre'D once on board and see what can be done.
Have a great cruise
Tuesday Chat Host