IF your vacation time isn't so precious that you can't stand the thought of some days not being what you'd pick for your days off, and IF this isn't your one shot at Disney, I'd give it a whirl, warts and all.
1) your mom wants to share it with you (and PAY) and that doesn't happen every day
2) you are still the planner of the group, so you have some measure of control
3) not to be cheesy or maudlin, but my extended family trip of 12 people (which, of course, many DISers warned against) turned out much more magical than not. And despite the fact that my dad had been ill, made a fabulous recovery that was part of the reason for the trip, he took ill again about 9 months later and passed away last Christmas. I cannot express how thankful I am that we made the trip, weathered the bumps, and have those memories and photos to treasure.
Lots of good advice above for setting expectations. I'd try to et them to vote on ADRs, or at least give you parameters. If you can't squeeze in all your personal favorites, maybe you can do an extra table service without them one day. Caution about assuming character meals are best for kids - my nephew was TERRIFIED of characters at that age. Screamed and cried at the sight of Easter Bunny, Santa, story time characters at our museum. We did a couple character meals with him that the other kids wanted, and he did okay since we didn't make him get near them, but if we were going *just* for his benefit, it would have been a bust!
Definitely get the Memory Maker and take lots of photos together!