HI KIM!
I have a big suggestion that I hope will help you. I don't know what airline you are flying and they all give different weight to requests, but call the airline ahead of your flight. I usually buy tickets on line and if you do so from Travelocity, Kayak or one of those discount sites and they allow you to select your seat, don't suppose that is where you will be sitting. My RSD is full body, so I need to stand and move, when my pain says I need to move. I ALWAYS request an aisle seat, so that another passenger doesn't trap me and keep me from getting up. I am fairly tall, so I need to get into the aisle to not be hunched over. Buying from a discount site doesn't secure your request for an aisle, only the ticket price and a seat. Ifyou can, buy Directly through the airline, they do secure your seat request. Otherwise, after a percentage of seat locations are secured/assigned, then its the gate agents who have the power to move you or secure a specific location. they can not even do that when you check in, at some airlines and its very frustrating to find this out when you show up for your flight.

Once you get your ticket purched, Then call them. some airlines have a dedicated phone line for people with a disability, i know United deos. Tell them you have a neurological disorder and that it affects your circulation and that it is excruciatingly painful. With circulation being an issue for clotting and stroke on planes, they will do what ever they can to accommodate you. When I sit with my legs on the floor and not elevated, the pressure builds up and I get this horriffic constricted pain, so I have to be able to stand and move. I have gotten stuck and not called in time to get them to address this for me and it worked out but it's really stressful not knowing you will be comfortable until you speak to the gate agents.

Because my right arm is my worst area, I bring a very soft bed pillow, it's really helpful in supporting my arm and giving me a soft thing to lean on. If you get in trouble with the number of items you are carrying on board, put your purse in your pillowcase, or something like that, just to board. I do it all the time. Make sure you have break through pain meds where you can easily reach them and once you get through security always get a bottle of water. You never know if the plane will load and then sit on the Tarmac for an hour and the flight attendants will be asked my the captain to stay seated. You need to be able to help yourself and reach and take meds without anyone helping if at all possible, but if you get in a bad spot, by all means, ask for help. I had a flight attendant bring me a small cup of water once while the plane was loading because I lost track of time waiting and was hit with really bad pain, earlier than I expected. SE was awesome but I honestly could have ended up waiting 1/2 had she not been so kind.

Mostly call the airline ASAP, most can flag you as a possible assist needs passenger and when you are out of your home element and have no control over the situation, being able to get help is a must and will make your flight a lot easier. And make sure you wear slip on shoes... It takes a lot longer to get through security with RSD, it does me. If your connecting flight is at a big airport that you are unfamiliar with, consider asking for a ride on one of those golf carts. 1.5 hours is a nice amount of time to change planes, but if your flight is late or you feel horrible, just ask. I am usually happy for the movement, but if you feel strapped for time, ask an attendant before you land and they can have someone pick you up and take you to your next gate. Flying is stressful already so your getting ready ahead of time and asking questions is a great idea.

I hope you have a great time at your sister's wedding
Soft hugs, Sylvia