You do not have to pay a trail fee in winter to use the hiking trails, I have climbed 3 different ways in winter & never paid
There is a family/group campground in the park near the Sun Bowl lift/ Rim Trail start
http://www.srkg.com/trail01map.htm
Several trails are not described, including the Rim Trail which goes through old growth forest to White Ledges and the Summit Trail from the ski area which is part of the SRKG Trail
Dartmouth-Sunapee Region > Mount Sunapee > Additions and Corrections