I didn't say about a stolen kiss. She may very well accept it. Why should it be a stolen kiss? History can very well evolve from this point. Sophia accepts the kiss. It is dramaturgically coherent, it does not violate any rule of the story. Sophia has clearly shown that she is intrigued by Dylan's attentions and therefore it it may be very well that at some point she agrees to please to her son as a woman. It is a plot twist, of course, but a legitimate plot twist and it can work very well.It has to be an accepted kiss from Sophia. Get her involved. Not a stolen one. To get to the sex later.
What you propose is for a girlfriend not your mother.