three day trip in car planning (Kanto Region)

hello
we have booked car for 3 days (30th july to 1st August)
But didint finalise the place of visit (Shortlisted only Nikko)
not much interested in Temples, any place which can take away from Tokyo Heat,

- Nikko + Tobbu world square + lake chuzeji (including nearby falls) day 1+ half day more
- ??
- ??

Me, my wife + my 2 yr old daughter in a car,
If possible please suggest some hidden treasure place which enrich our road Trip more,

We need to finalise the places, so that we can book hotels in advance, ( my wife prefers Veg. food)

Please suggest a good place

Kinugawa Onsen close to Nikko have a few attractions which might be of interest for you:

http://www.japan-guide.com/e/e3875.html

Kairakuen garden in Mito may be of your interest, also beautiful Oze National Park is within reach.