I have ridden there many times, and it is a good place for the family. The majority of the bike trails are the cross country skiing trails. As such, and since it's in the mountains it does have some climbs, like up the back side of Snow's Mountain, or up from the Town Center to the WV main ski area.
However, you can make a route that is relatively flat if the family wants one, more or less along the streams that run through. Best place to enter these trails is on the road to the left after the tennis courts.
Snow's is lift serviced and technically a downhill route, but doesn't really compare with other lift serviced venues in variety, challenge, etc. It pretty much just goes down the beginner ski hill.
There's a nice little town center, easy to walk around, and stuff for kids to do. The gym and pool there are also quite nice and generally are included with condo rentals.