Even an adult would enjoy the Polar Caves in Plymouth, The Flume in Lincoln and even Lost River!! You can go to
http://www.visitwhitemountains.com/t...tion-pass.aspx
and get an attraction pass which allows you entry into 16 of the White Mountain attractions! It's a great deal but if you're only staying 2 weeks then at least check out the site and get an idea of what is available for a short drive away!!