We were in the Marriot Mountainside Hotel in Park City, UT for one week. It was a beautiful resort in and prime location to all activities. You can walk into the old town either along the street or walk over a block to a walking path and walk along a beautiful creek.
There is a swimming pool, and hot tub on property, but is very crowded with children. This appears to be a favorite location for family get together and family reunions. It appears the staff put the family groups in one area of the hotel, and other guests away from the busy active families, which we did not mind at all. We had a large 2 BR room and a very quiet location.
There are several activity rooms on the second level for different activities for all age groups.
The hotel is very well is located next door to a very large outdoor activity center. There are ski lift rides,(2), Alpine slide, Alpine coaster, mini golf course, 2 merry go rounds, rock climbing wall, 2 different styles of zip lines and more. It is very busy and can be expensive.
If you like to hike of mountain bike you can take the ski lift up, round trip is $12 per person, but you can get off at the top and hike for hours or ride your bike on numerous trails. When finished you can then go back and ride down.
There are a few restaurants open in this location as most of the business is ski business and they are closed for the summer.
It was a great stay, beautiful and lots of fun. I would recommend it to anyone for a pleasant vacation with or without children.