i don't know much about Montana, but I would highly recommend Glacier for family vacations. We spent a week there a couple of years ago. We try to do a National Park for a week, hopefully more in the future. This will be the fifth year, and I think Glacier is right up in the top spot as far as favorites go. Kalispel and Helena are pretty cool towns, not sure what you are into, but we really liked the area. Just kindof drove through town. The fall is one of the better times to visit Yellowstone, IMO. The crowds don't seem as bad after school starts and the animals seem pretty active. Some of the facilities in both spots shut down early, but I am not sure when exactly. As far as antelope goes, I am not familiar with Montana, but it sounds like you have some good advise there already.