.. why don't we take Mom right after you get out of work and dump her off then go to the movies!
Jak, I would certainly mention how happy you are that he wanted to spend time alone with you after dinner with mom. He is doing a nice thing for his mom, but he also is letting you know he realizes you two need time together. Pretty amazing if you ask me!!! (or at least comparing what my H would have done in the same situation. I would have been the one inviting his mom to dinner and begging H to go along. Then I'd be the one initiating the movie, but he'd rather go have a beer with his brother.