Grouper is probably gonna eat all 3 of your nice lil guys. If you want a grouper that bad return those 3 to the fish store and see if you can get some money for your grouper.
If you are thinking of putting those fish in a 65g, forget about it. Like Treble said, they would all be snacks for the grouper. Stingrays vary in care level and are usually suited for only advanced aquarists. Bo