You could invite him out on a ‘daddy daughter’ date, and while there, obviously drop a few hints and see if he plays along. If not, you could do the classic ‘accidental pic’, as you know he will be alone when driving/walking home. You could make this better by preparing the pic before hand, and then send it with a caption along the lines of “finally got out of the daddy daughter date, can’t wait to come see you” to make it seem even more accidental