Thank you all for answering my previous questions. I think we have decided my mother in law will be most comfortable in a regular wheelchair. I am planning to rent from Walker Mobility (assuming they deliver to my hotel) but they have a bunch of different sizes. The info says 240 lbs and under for an 18 inch wheelchair. MIL is definitely smaller than that. Is this going to be comfy for her?
If doubting; remember that wheelchairs are not like a chair at home. These ones are best when they fit you instead of leaving heaps of space left on both sides like you might very well buy a comfy chair for home. Still doubtfull? You can always ask Walker what the seating pitch is with both depth and width. Meassure up what MIL needs. And see there; you will know for sure it is not too small for her. But she should be fine.
I have read here that we need something to cover the seat because of the heat and rain ponchos in case of rain. Should I get some type of pillow for her to sit on?
Would be much more comfy, yes. Esp. with recovering from a broken hip. These chairs fold up by folding up the seating itself. So basically see would be sitting on "tight" pulled fabric. You most likely can imagine that is not the most comfy. Try out at home what she finds most comfy in cushion or pillow. Something as simple as a smooth anf soft towel is enough to cover the back from sticking to her and being uncomfy sweaty.
But how about the travel, are you driving of flying? In the latter, consider renting a chair at home and bringing it along. It's free of charge and would prevent her from ending up "biting the bullit" and walking more than she should. Yes, airports have chairs to use, but first come first serve and that doesn't do the trick if she finds the need to sit down before or after using said airport wheelchair. You can bring it along on the flight free of charge and does not count towards her bagage allowance either.
Thanks so much!!! MIL only used a wheelchair for a brief time period after she broke her hip and I was not there with her so I have no idea what is best!
Doubtfull she has either.

Downside is that for these shorter term needs they tend to "shuv" folks into the most basic of basics. It'll do the job for the mobility need but comfy is definately not a way to describe it. And when using one for the first time, it isn't always easy to know what you can do to comfy it up.
One more question.....if anyone has dealt with a broken hip before. Do I need a handicap accessible room? She will not use the wheelchair in the room but perhaps she needs a handicap accessible bathroom to help her there. Do normal hotel rooms have bars on the shower or toilet? I honestly cannot remember. I hate to sound like a total idiot but I am trying hard to plan so that my mil is comfy.
Depens on what she needs. If she needs grab bars; that would require an accessible room. There are 2 styles; rooms with grab bars (totally the same as any other room, but with grab bars in the bathroom) and fully accessible rooms with a roll in shower instead of a tub (also will have grab bars). If it suits her best, you can also ask for a showerseat when booking a room with only grab bars. this can be put onto the tub, transforming it into a tub with seat. That would mean no longer needing to step into and out of the tub, which can be risky because of slippery and a pretty hard move when recovering from a broken hip for some. If that might not do the trick; go for a room with roll in shower. That way she can roll the wheelchair into the bathroom, for both toilet and shower and just transfer onto either toilet or shower. Be ware though; this is a set up where toilet and shower are not fully seperated by a door, so using the toilet while another one is showering might not be desirable depending on relations.
Rooms with grab bars do have that seperation but she would not be able to roll the wheelchair into the batroom itself. Take a look at the sticky about HA rooms, locations etc. There will be all kinds of pics in there so you can get an idea of what you might expect. It does differ per resort when talking about lay out etc, but the basics of "roll in shower" or "grab bars" will always be there so to say.