My mom is gone now and my Dad's an invalid, but I was/am their fiduciary. Some years ago, when we were reviewing their finances, I was shocked to discover that they were earning more in retirement than some of their children who worked full time. Plus they had a paid-for, new-ish car and house, along with cheap property taxes, excellent medical insurance (Go GIHA!) and a Federal pension, complete with COL adjustments. I gently pointed this out to my mother. She shot right back with "Oh, but you guys could go out and earn more. We can't do that, so our income is fixed." OMG! Deluxe face palm!!!
The problem wasn't with their income, it was their perception of scarcity. If you think your parents might be caught in the same trap, as many parental-type folks are, stand your ground.
If there really are genuine financial concerns, do you have a nearby friend with a guest room? When we have large family gatherings at my sister's house out in the country, we stay with a friend of hers who has a very large home. We love it and them for accommodating us so graciously. Of course, she knows that our door is always open, should she or any of her family need a place to stay in our neck of the woods.
If that's not an option, do you have hotel points you could redeem?
We love the Holiday Inn Express Points and Cash Program. Basically, you can buy extra points and add some cash to get a great deal on a hotel room. On our road trip last weekend, instead of paying $119.99 plus a shitload of taxes, we paid $40.00 and 5k points, with zero taxes. Because we have Elite status, we get a 10% rebate on points spent and we always take the 500 points in lieu of the "Welcome Amenity" which is a bottle of water and a high calorie, low nutrient value snack. So net/net 4k points and $40 oop per night. Score! This may not help you today, but it might for future trips. If you know they'll be visiting again (check) and there's a decent Holiday Inn property (or any of their many brands) near you, it might be worth checking out their affinity credit card and collecting some points for future visits. And no, I have no connection to IHG, except that I stayed in their hotels during my working years and amassed a shitload of points, which I am stretching as far as is humanly possible. DH got their CC last year when they were offering a boatload of points to enroll, so we both have whatever their new, highest status level is called. Plus, each of us gets a free night every year with their CC, which more than covers the annual fee(s), especially when you redeem it for an Intercontinental Hotel in a lovely resort area. The annual free nights have a small window of overlap, so every other year, we can have a nice four-day stay at a lovely hotel between Christmas and mid-January. Sweet!
FWIW, I hate air mattresses. Sleeping on one attempting to sleep on one totally blows, IMO.