I posted about this a few months ago. I was anxious because FIL was making noises about coming to stay from overseas around the time when our baby is due/very small. And I just didn't want visitors, even family, actually staying with us with a newborn. We already have four kids between us and life is full-on without looking after a new baby and a house guest too.
I wanted to hang out in my PJs, establish breastfeeding, skip make-up, get over any baby blues, sleep whenever I can, etc, until I felt ready to be presentable to the world. Plus I'm naturally introverted and private, and don't want the world and his wife over anyway after baby's arrival and want some significant quiet time; even without baby in the frame, I'm of the any-house-guests-stink-after-three-days philosophy.
In the end we emailed FIL to say, very nicely, to hang fire with making any arrangements and let us consider when would be the best time for a visit. DP also spoke to him and said due to limited space, he'd probably have to stay elsewhere and visit in the day (this would at least take the pressure off us to be on top hosting form when least feeling like it). FIL seemed to get it and DP left things at, "I'll speak to Frugal15 and we'll get back to you."
Fast forward to now and I'm overdue and booked for an induction this week. Meanwhile FIL got on and booked flights anyway and will be arriving at the end of this month. Now, he and one of his other grandchildren (aged 10) will be coming. They'll be here for close to four weeks, not two (as he'd originally suggested). And when we've asked him what his budget is for accommodation so we can look at options locally (initial plans to stay with relatives locally haven't worked out), he's said he doesn't have one as he's already overspent. He's suggesting we put a tent up in the garden if we can't fit them in the house. 
So, baby will now be arriving within the next five or so days, and we're now looking at DP spending his paternity leave buying and building a bunk bed, shunting furniture around, and making space to squeeze nine people into all four corners of the house, so that FIL and one of his other grandchildren can stay for nearly a month from when the baby is less than a month old. AIBU to find this an horrendous prospect?!
While they're here, I'll feel like I need to keep the fridge well-stocked and the place tidy, get dressed every day, stay up when I want to nap, cook, be on form conversationally when I've had an absolute fucking fill of small talk, have the telly on for baby's cousin when I want peace and quiet ... argh! Is there anything we can do? I don't want to seem unwelcome, and I don't want to offend FIL by telling him to bugger off. Of course they want to meet this new grandchild/cousin. But every day and night for a month is too much - way more than your typical, more thoughtful couple-of-hours-pop-in (not possible with the distance, obviously).
I feel that FIL has forced our hand and I'm bloody pissed off that any plans we might have had for how we'd spend baby's first few months, and how I might take care of myself once DP is back at work and - importantly - try to prevent PND (I had it mildly with my first DC years ago), have been completely overwritten. DP is fuming and currently stomping about the house swearing, threatening to give FIL an earful and tell him to cancel his trip. I'm saying hold fire with that until I've got some advice ... anyone?!