Snow near Osaka in mid-late December

My family has visit Tokyo - Osaka - Kyoto a couple of times but wanted to do something different this December by visiting Hokkaido! However we are too late to book / redeem the air tickets as it is a popular destination in December. The flights are very limited and the tickets are crazily expensive.

We were even thinking of flying domestic in Japan to Hokkaido but then again the ticket prices are crazy. If we were to take Shinkansen to Hokkaido, we are required to change the shinkansen a couple of times - we have 2 kids and will be bringing a few luggage.

I am thinking of the following destinations for 10-14 days in mid-late December - not all but need some advice to narrow down.

My family loves theme parks, adventures and food! Since we are from a tropical country, we would like to see snow too. For theme parks, we would like to explore other than USJ / Disney.

Could any kind souls please enlighten me? I am so torn!

Osaka
Fukuoka
Kyushu - Beppu
Nagano - Jigokudani Monkey Park

Most if not all airline companies start to sell December airticket after late August (maybe 26th). I think if it's normal weekday, the airfare for Osaka (including Kobe, Itami and Kansai airport) to Sapporo (Shin-Chitose airport) will be 5000-10000 yen.