You need 60K for a r/t reward in coach, and 100K in business if using UA's program.

Also, it would not be easy to get 3 business class seats on the same flights unless you book months ahead. Even that, you may only find 1 to 2 business class seats.

AMEX MR pts currently running a 50% bonus bonus for transfer to BA which tends to have excellent availability because BA charges hefty YQ on its awards which are priced by segment. If you are willing to shell out the YQ, BA actually would be a good option due to the 50% transfer bonus (ends on May 31st) and the excellent award seats availability, direct flight from West Coast.