Last year in the end of Jun, i went to Osaka->Hokkaido->Tokyo for 14 days with my kid (3.5yrs) (without driving). I was bought ANA package, airfare to Sapporo w/ 2 nights hotels. I like their flexible regulation, ie., 2 free stops at Osaka & Tokyo without additional charge and the maximum travel days is 15 days. As some package/special airfare is within 7days.
Let me send you my itinerary tomorrow or later for reference. Pls pm me yr email addr!