Although I really enjoy summer vacations at Mountainside, I have encountered problems with crowds and unsupervised children. There are many owners who live nearby and use it as a summer getaway. They often have other family members come on the weekends to use the facilities. This appears to be a bigger problem from Mid-June to the end of July. Weekends can be bad, but weekdays seem to be less of a problem. When I was there last year around Labor Day, this was less of a problem and MVC staff appeared to pay more attention to keeping unsupervised children out of the Fitness Center. It is a shame that parents don't respect other guests or the safety of their kids.
I have observed that guests here frequently take over the grilling areas. I don't think these are outside groups, but are owners who are staying there and using it as their own 'summer home'. I've observed people putting tablecloths on all of the tables at lunch time, and then staying throughout the evening. They hog all the grills and tables. To be honest, I've not encountered this selfish behavior at any other MVC property. During one visit a few years ago, one 'family' used most of the tables for most of the week. They have expanded the grilling area and added more tables, but there are still some local owners who seem to think the whole area is there for their own private parties.
We still really enjoy the area and have learned to work around the grill/patio table situation and now go either early June or after Mid-August. It is really a nice getaway from the heat and humidity of the Midwest. Since it is a ski resort area, there are several excellent restaurants which offer more reasonable prices in the summer. Sundance and Mirror Lake are within about an hour drive and scenery is comparable to national parks (and a lot less crowded).