If you have a healthy and at least pseudo adventurous sex life as it is, I'd say avoid this situation. Sounds like they "need" you, which will translate into them taking advantage in ways other than that which you might be happy about. Now then, if the answer to the preceding question is "no," then I'd say go for it, and pay the drama piper later. Doc, I know you said you're married, and that you've had other girlfriends... but are you sure you aren't gay? Not that there's anything wrong with that, but that sounds like something only a gay guy would try/could get away with. Especially the "Sweetie" part.
Alright here is what you do. You leave this thread open on your computer when you are moved in. Specifically on the part where you dont want to sleep with them because you dont want to hurt them or yadayada ya. Next thing you know, they think you are a sweet guy and there sex drive is switched on to auto-lay. Good thinking stipendlax... good thinking...
Don't think I ever mentioned hurting them... but your ideas are intriguing to me and I wish to subscribe to your newsletter.
The sad thing is I was seriously seeking advice at first. Granted, I did it but after that... wow, talk about derailment.