Thanks for your reply jackieq513! We ended up going to the Urban Kitchen at Dusit Thani. The buffet was so amazing!! I ended up not eating any turkey at all. :)
I noticed the St Regis on Saadiyat were advertising Thanksgiving dinner in the steakhouse, 55th and 5th and I think the Holiday Inn were also doing a Thanksgiving brunch.
The Westin is having a Thanksgiving dinner tomorrow night - I had xmas dinner there before and it was very good. Also seen an ad for Rodeo Grill at Beach Rotana hosting Thanksgiving dinner.
Hope this helps - be worth a google on these or check on Time Out Abu Dhabi for other ideas.