You (well, Angel Flight) will need specific approval to use flight numbers - and it's not easy to get that approval.
I don't think there's a problem with saying "ABC Angel Flight Baron ...." - ATC might give you a little help on the way in/out, but I don't think Angel Flights qualify for any priority.
Don't try to use "Angel Flight 1234" unless Angel Flight have approval to use flight numbers - trying to do so will cause you grief
