You already have the answer to this question, you're looking for validation at this point.
1) Pick one, drums, trumpet, or singing. There are only so many hours in a day and the trumpet isn't a forgiving instrument. If you don't have the time then lose the drums, lose the trumpet, lose the vocal leads or be satisfied with how you are.
2)While it's good to have a goal, don't pick one that's unreasonable. Your goal for trumpet should be hard but attainable and the time needed to learn should also be reasonable. Or, is your goal to be the drummer or the singer?
While it will be hard because people depend on you to sing and play drums. You got yourself into this predicament, get yourself out. Lop off the silly stuff and get back to the discipline of trumpet. You're a trumpet player for pete's sake.