It really depends on your Mom's physical capabilities and if she even likes to ride rides. When we used to take my Mom after she got older she wasn't able to walk a lot so we pushed her around in a wheel chair and I don't think she rode any rides. She would just wait with my son when he was too small.
I'm 65 and in decent shape, if I were to skip a park it would be HS and not AK but I love AK, it's just so peaceful.
As far as rides, I have bad hips and a bad back/neck so I don't ride RNRC (the launch kills my neck) I do ride ToT, I'm been known to get off and right back on. I ride RoTR sometimes but it's not a must do. I haven't ridden Star Tours in years, it makes me sick and I haven't ridden MF much lately. My last trip I didn't even step foot inside of Batu. I like SDD, it's an easy coaster and I do TSMM. I've ridden MMRR a few times but it's not a must do for me. The dance scene kind of jerks you around a lot (especially if you are smallish) and it can hurt my neck. I love all the shows, Indy is my fav. but they have modified it so it isn't as much fun as it used to be. I love HS at night at Christmas, they use retro decorations and it's so pretty.
Epcot can be a challenge to walk, I've been known to go back and forth across the park more than 3 times in a day and the last time I usually take the boat. She would probably enjoy just walking around the countries and going in the shops. Of the rides, I pretty much like them all except Frozen (I don't like the movie but oddly I love the show at HS) and the Mexico ride. I'm bitter they changed it and put Donald Duck in it. I love the Land and love walking around the Living Seas, I usually skip the ride.
If you have time, take her over to GF to see the tree and gingerbread house there. All the resorts really do it up for Christmas.
MK is what it is, not my favorite park and I usually just do a half day there but it is beautiful at Christmas. Stay away from Space Mountain, it hurts. BTMR can be a bit jerky, I can ride it but my son who has nerve damage in his spine can't. SDMT can be a little rough but it's doable.