Yes, this will be listed on the Daily 'Iwa. You can view the 'Iwa online as well. It seems like the full week shows up around Weds-thurs of the previous week online (but is subject to change). I am sure the Animation class will be offered over the holidays, its just a question of which days you're there and that coincides with their schedule.
When we were there last week the Animation Class was offered on Thursday from 12-1 and 4-5pm. You will need to go to the Pau Hana room and sign up first thing in the morning when they open (8am), though, so factor that into your plans as well unless someone else in your party can do the sign up while you go to the spa. For example, I had a 9am spa appointment (but you're supposed to arrive at least 45min early) one day. I went to the Pau Hana room to sign up for the ukelele lessons on my way to the spa and even though I got there and got in line around 7:50 the sign up still took a few minutes and I didn't get to the spa until 8:15ish. I was definitely wishing I had a few more minutes in the hydrotherapy garden before my appt.