Grandparents won't visit newborn twins
Second, there's the offsite-housing problem. To mitigate that, express whatever regret you can honestly express: "Of course we'd want nothing more than to have you/everyone stay with us as usual. All those babies took care of that, though."
The second message is actually best delivered by your wife. They see you as the ogre who doesn't want them, so you issue the invitation; they don't see your wife as pro-hotel, so she insists on the hotel. Present a pointedly united front.
It's no guarantee, of course. People who want to believe something will do so despite any and all evidence to the contrary. (Ahem.)
But you can make sure their only options are either to rethink their position based on new evidence, or to cling to it with little valid defense.
You can also, of course, just host them in the condo, but on a superficial level that's a decision to invite sleepless chaos, of which I'm sure you have more than enough right now. Routine is often all that stands between parents of multiples and the emotional cliff, and it's hard to think of a more effective routine-buster than houseguests in tight quarters who come with specific expectations but don't use their words.
Speaking of -- if your in-laws do ever visit, I hope you can invite them into your routines so they can see how things work, feel invested themselves, and maybe gin up some empathy.
Anyway. On a deeper level, housing your in-laws in the condo would be a choice to appease the irrational people who are complaining about you behind your back, which is a step you should neither take lightly nor without your wife's full agreement and support.
You'd have to agree (1) that it's worth it to you (meaning, yourselves, each other and your babies) to make a onetime exception, and (2) that you're both strong and committed enough to put the boundary back afterward and keep it there. If the boundary is still needed, that is; one weekend in a fishbowl with four adults and two babies might be sufficient to prompt your in-laws to have an ideological conversion on the matter of bunking as one.
The decision to try this is a lot to manage. Think and talk it through carefully.
If it helps, you won't always have to manage exactly this problem under exactly these circumstances; time means change, and change is rarely plainer to witness than in children. A hotel now doesn't mean your kids won't know their grandparents ever. (And if it does, by some fluke, then that will have been said elders' choice, not yours.) Your problem now is in many ways a problem only of now -- and it's OK to see it that way as it suits.
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