My Mom has knee problems too, so I know exactly the kind of worries you are having. My family stayed at Paradise Pier for our recent trip and we loved it...but I will be honest. The walks did seem longer than I was expecting. Don't get me wrong, they are not very long...but with a Mom with knee issues, especially after trekking through the parks all day....I think it might be tough. DLH is at the complete opposite end of Downtown Disney from the entrance plaza to DL and DCA. It is a very enjoyable walk (music, people watching, never leaving the "Disney" vibe) but it is a decent walk with little ones or a Mom-with-knee-problems after a long day. We stayed 3 days at PP and 3 days at Howard Johnson's and to be honest, I think our walk from HoJo's was quicker...and DLH is further than PP. I know my Mom is always too proud to do the wheelchair thing....but there are companies that will rent them to you and have them delivered to the hotels. Is it possible to do that and then at the end of the long day, someone can meet her with the wheelchair for a nice stroll back to DLH? You could also take the monorail from inside the park and it will take you a good stretch of the way, which would help. Staying in a Disney hotel was great, so you may not want to skip that...but I would definitely be sure that the walk is not too long for her. Good luck!