In Osaka itself, there is the Kaiyukan [Osaka Aquarium] which houses a large array of different species of marine life. From penguins to seals and with the center piece being a large tank that houses a couple of whale sharks! [
https://www.japan-guide.com/e/e4004.html] I highly recommend visiting this aquarium!
Then for theme parks, you've got;
- Universal Studios Japan
https://www.japan-guide.com/e/e4021.html.
- The Legoland Discovery Center Osaka
https://www.legolanddiscoverycenter.com/osaka/en/Museums, there is the Osaka Museum of History [
https://www.japan-guide.com/e/e4014.html] and also the Osaka Science Museum [
https://www.japan-guide.com/e/e4015.html]
If your children like Pokemon, then there is also the Pokemon Center DX and cafe that is between Dotonbori and Shinsaibashi [
https://www.pokemoncenter-online.com/cafe/en/?id=access]
Advance reservation is required for the Pokemon Cafe.
And there is also a 2nd (and smaller) Pokemon Center located at Osaka Station in Umeda.
Further afield from Osaka, in Kyoto.
There is the Iwatayama Monkey Park that can be found in the Arashiyama area of Kyoto.
Kyoto also has;
- Kyoto Railway Museum [
https://www.japan-guide.com/e/e3972.html]
- Kyoto Manga Museum [
https://www.japan-guide.com/e/e3946.html]
- Sagano Railway [
https://www.japan-guide.com/e/e3965.html] *This is in Arashiyama.
- Kyoto City Zoo [
https://www5.city.kyoto.jp/zoo/lang/en/] *2nd oldest zoo in Japan.
- Kyoto Pokemon Center
As for the snow... There is a small chance of snowfall in Kyoto and the surrounding areas during your visit to Japan.
However, it isn't guaranteed. But if there is snowfall during your time here, then I would certainly recommend visiting Kyoto's shrines and temples during this time (especially Kinkakuji, Kiyomizudera, Arashiyama area)
The best place nearby, for most likely seeing snow, would be Koyasan [
https://www.japan-guide.com/e/e4900.html]. However, the conditions (snowy paths) could be risky for both your children and yourself, and I would advise extreme caution.
