We went to DL for two days and then went for a week to the Marriott time share in Palm Desert as well! Small world! We went last year for Thanksgiving.
The Zoo has a beautiful holiday display called Walk the Wild Lights. It wasn't very expensive, and had a ton of beautiful lights, an area with food and bands and open pit warming fires. The last day is 12/31. I'd go if at all possible.
http://www.livingdesert.org/calendar/edetail.asp?id=166
Boomers was mentioned, but we didn't get there. The holiday got in the way.
We went to a movie one afternoon at the Regal Cinema right next to I10.
There's lots and lots of shopping.
Just about anything you'd want to eat is there.
Marriott will probably have a number of activities, including various crafts, family movie night, and they also had a Texas Hold Em tournament, which both my sons and my DH participated in. DH actually won the tournament, and he got $25 g.c. to be spent on property during our stay.
While we were there, we rented bicycles for an hour and the entire family (including my parents, my kids, and my bro & sil) all went bike riding. That was fun.
We brought a few games, including Mexican Train and scrabble (I splurged for the travel version of scrabble so we could play at the pool.) At various times during the week, we played games.
Not an activity, but a suggestion.....either bring or purchase when you're there, a crock pot. There were too many times when we were confined to the condo because we needed to cook something for a meal. By bringing the crock, we could have dumped everything in in the morning or before we headed to the pool and not had to worry about it.
I ditto the tram, I loved it.
I don't think there will be fireworks, but I could be wrong. The Marriott Hotel in Palm Desert has a number of activities that are open to guests at the condos. I'd give them a call. The second night that we were there, Santa arrived at the Marriott and in a standing room only extravaganza, they had activities, and music and Santa visits, etc. They had fireworks at the end. They may do something similar for New Years.
New Years is a crazy busy party time in Palm Springs, just to warn you. Lots of drinking and partying. I'd go to the Zoo for the Wild Lights and go back to the condo early. Or, make reservations (most of the restaurants in the area take them, and NY will be busy!) and eat after going to the zoo but get back to the condo before it gets insane.
Here's a website that has lots of info:
http://palm-springs.org/
and
http://www.palm-desert.org/