20 day itinerary help with kids Hokkaido, Tohoku, Kanto & Chubu Prefectures in March

Taking 1 and 6 year old to visit in late February to mid-March 2023. We’ve visited the 3 big cities and famous sites before so these are less of a priority for us.

Highlights we are looking to see and do:

-Kaiseki meal, child friendly, prob find this in Tokyo, recs appreciated.

-Hokkaido for the fresh seafood, nature, and onsen. We will miss the Ice Festival unfortunately, hopefully we can make it up with a different site.

-Theme parks and museums Incl Disneyland/Sea, Anpanman Museum, Calico Critters/Sylvanian petting zoo, Sanrio Puroland, Miraikan.

-Do a Festival that is family friendly, hopefully involves fireworks, fire, lights or some other explosion (jk).

-Visit other prefectures for nature, onsen, and sites, this is where we need the most help.

For other prefectures, since we plan to go to Hokkaido, I am thinking it makes sense to visit Tohoku, Chubu, and the northern Chubu prefectures. We’d like to see nature like flowers and do farm visits.

For onsens, where will we find a private onsen in-room so entire family can join and we can change temperature, availability for end of Feb, and town scenery. I have research Ginzan and Atami, anything in Hokkaido?

Thanks all!