It makes no odds if you are staying in Doolin. Both courses are quite close. Lahinch is about 10-15 minutes and Doonbeg is only about 35 minutes. Ballybunion is very doable for a day trip. One problem, many private clubs do not allow visitors during Christmas break. If they do allow visitors, they may consider 27, 28 and the Jan 3 holidays.
The weather is easily playable in December-January. Just avoid the 5c with rain and 25 mph winds. It takes a nice long bath and several cognacs in front of the fire to recooperate. Not a bad way to spend the day!
Rick, Tom is right. Portstewart is certainly worth a game no matter what time of year.
Ciao
Sean