Traveling with MS

My family is taking the trip of a lifetime. We are set to leave for an 11 day cruise later this month. This means we fly from Boston to London and then catch the boat from Dover.

My wife has suffered from secondary progressive MS for 12+ years. She's wheelchair bound and has a superpubic catheter.

My questions for the community.

1. Have you done big vacations with your spouse/family member who had MS? What were the trouble spots?
2. We'll be on the plane for 6+ hours. Has anyone ever had to deal with emptying a urine bag? What did you do to keep it discrete?
3. How were the airports in handling the wheelchair/accessibility?

I want to make this the absolute best vacation for her. So, I'm trying to cover as many bases as I can.

Thanks in advance

Craig