We had a tree up last year and I have 7 cats also. Granted we put up a small Charlie Brown tree (real) and very limited ornaments only hung near the trunk area, but we had one including lights. The hardest thing was keeping them from getting into the water basin. I had to use simple sugar water solution rather than any other additives which might harm the cats if they should drink it.

Here's a pix of Cami lounging under the tree.