Under the current circumstances, I think MC would have an easier time convincing Nicole to have sex next to a sleeping John than convincing her to do it in that bedroom. Plus, considering that the Heavens family consists of only John, Nicole, and Chloe, I highly doubt those two would be forced to go to that exact bedroom because it's the only place they can have sex.
The only possibility I see it remotely possible in is that it happens quite some time after Chloe has fully recovered of her current condition and is already at that far-off college of her dreams (whose name is unknown in all possible routes). Right now, I see it as impossible, no matter how horny Nicole might get with MC.