Yea - stuff like this is easy to happen.
You seem like a great person - so the 'host' mode would seem natural. But you're right in not wanting to take that on all the time unless YOU are up for it. And after working hard all week, that's not always the case.
But that's just real ! And it's a simple, really, as sitting down and explaining it. There's no foul here - for anyone ! Like Mohegan said, hubby needs to understand this is primarily HIS guest and HE needs to host ! And in reality, I'm betting if you share this with her openly, being another woman, she'll understand completely and team up with you to put the pressure on HIM
Don't keep it a hidden frustration, just explain it with a grin.
As for the mannerisms difference between a NEW relationship and a comfortable one.....
I'd use this as a talking point to illustrate how relationships can easily (and frequently) slip into a rut. I think it happens to most all of us that have been in long term relationships. But someone or some circumstance needs to call it out. This can really be a good wakeup call. There's a certain expectation I think when things are new, and eventually I think all relationships 'settle' into a comfort zone. We WANT that - that comfort. The trick is though, to not let it 'settle' to the point it hits bottom. I'm sure you understand that if their relationship lasts, IT will start drifting towards that same point. Tis de nature of tings
Same with the sex. That NRE again ! A gentle reminder that it USED to be that way between you two and that you miss it (and he did to - whether he realized it or not) should be enough to bring some of it your way. But like the farting, remember that wild passion with her will eventually diminish. Nature again....
Smile. Be happy. Teamwork.