All I know is that Daval is running out of excuses for the sexual scenes and the characters are acting really dumb to justify it, like "son, your dad can't see that bulge in your pants, so I will blow you instead, but quick before your father comes and no, we can't close the door!" I like to think that Sarah isn't dumb, she's just slutty.
I think with David, Sarah was being provocative or "slutty," if you will; with Uncle Peter, Sarah was being naive and gullible; with Aaron, I think Sarah is just being dumb, because Daval is writing this set up poorly. I think Daval wants to get Sarah to do things with Aaron that we haven't really seen her do with David or Uncle Peter, i.e. drink his semen, and intends to facilitate this Aaron/Sarah pairing regardless of how haphazard the lead up is. Remember, Daval wrote Alice having her first "on-screen" sexual experience (little to no resistance performing cunnilingus) with some random woman in the bathroom where she works. And for what? To set-up the Uncle Peter comic.
I think many of the fans won't put much stalk into this lazy set-up because of how highly anticipated an Aaron/Sarah sexual encounter is. David fans should be in an uproar, but they're not. And this goes only to inform the point I made some time back that the Uncle Peter controversy wasn't primarily rooted in his random introduction, even though I agree it could've been handled better, or that some guy paid Daval to put his likeness on to this work; Uncle Peter is just as related to Sarah, as Sarah is to David. And granted, Sarah's son bears a stronger relation to her, but he's still a male other than David. And I would expect that Sarah's father, if Daval means to go through with his stated initial intentions, will join the fray at some point. It's because Uncle Peter's old, and doesn't bear a strong enough relation to her to disrupt the already established relationships. There's no Oedipal fantasy with Uncle Peter, and is probably too old a character, with whom most of the audience can identify. When Sarah's father enters those sugar walls, won't the reaction be the same? Well, no... because it's her father, and there's an Electra (opposite of Oedipal) fantasy, there. The irony is, the Electra fantasy was just as present in Sarah's interactions with Uncle Peter, as the Oedipal fantasy was in Sarah's interactions with David. I think the fan base was just too caught up in their anger for it to register. Anyway, I'm rambling (what's new, right?)
As far as how this scene may proceed. I wouldn't be surprised if Sarah and Aaron have sex in the next update. Luke will probably leave the room, and Aaron will have another erection at seeing his mother swallow his cum while she's a top of him. Sarah with her infallible logic will probably state something like, "you can't have an erection if your father comes back to check on you, so... close your eyes." Funny enough, I actually like this approach of Sarah performing these acts while not directly looking at her son, as grk alluded.