He's rather about to give up on getting anything but a few kisses and maybe a quick tumble next shore leave, when William's text comes in, pointed and entirely correct. The few moments it takes for him to just stare adoringly at the words give enough time, apparently for Horatio to respond.

Well. This wasn't quite a conversation he was prepared to have just yet, but if it happens...

You two gentlemen do know where I'm at.

Alternatively.

Or I suppose I could meet you somewhere.

Maybe it will come to nothing. It might be nice, at least, to get it off his chest and have it aired out between them.