I would prob just not reply to that message OP. besides, if he's so busy there's no point offering to take DD out there as his reason for messaging in the first place was to tell you he is too busy to come see DD.
But I'm not the best person to he giving advice right now - I just told DS's dad off as he has cancelled whenever he feels like it lately (the last year!) yet sent me a message 'telling' me (not asking me) just when he'll see DS. I let loose on him, effing selfish twerp!
So yes my initial reaction to your OP was tell him to sod off but I decided to stick with ignore the message.