"Mm," Charles says, which is itself a deceptively quiet thrum of nonsense noise as he shimmies up Erik's chest and wraps his arms around his shoulders, and it's simply easier to kiss him straight on when Charles is straddling his lap, so that's what Charles does. He briefly turn somewhat to hitch the blankets back up around his waist and Erik's sides, but beyond that he trusts to the heat of Erik's skin to keep him warm.
"What if I told you I have high standards for everyone and simply don't let them know? Would you believe me?" Charles smiles as he traces the corner of Erik's mouth, sitting peaceably in his lap with no efforts to escalate beyond where they are--although there's an easiness in his limbs and the languidness of his smile that suggests he wouldn't mind even slightly if Erik chose to do just that.
He kisses Erik on the mouth again, gently, because it's a good thing to do. It makes him feel safer and more whole, and at a time like this that's even more priceless than it usually is, although he knows that 'more priceless' makes absolutely no sense. It's still true, in a way.