Honeymoon Trip To Hokkaido

Hi, we are going to Hokkaido for our fly and drive honeymoon soon. Can someone advise roughly how much expenses per day assuming decent lunch and dinners? Any other advice about Hokkaido as our first time there? Thank you.

It widely depends on what you understand under a "decent dinner". I estimate:
1,000-5,000 yen per person for a decent lunch
2,000-20,000 yen per person for a decent dinner

Some basics:
http://www.japan-guide.com/e/e2410.html