Traveling Summer 2025 with 3 teens

We are looking to plan a 2 1/2-3 week trip starting mid June-start or July with our family of 5 (including 3 teens). Looking for best Asia destinations that aren't scorching hot as our kids/family definitely doesn't thrive in hot and humid climates. We traveled to Thailand and Cambodia last winter, and we've been to Bali. We've also done a decent number of trips to Europe. Japan is appealing in general but so incredibly pricey, hot and crowded in the summer. We are active, adventurous and appreciate culturally immersive experiences for the kids to see and experience other ways of life. We would greatly appreciate suggestions in addition to any itineraries or travel planners you would recommend. I typically plan trips myself but my schedule is a bit tight right now. We are also open to Africa (though I just read you're not supposed to post in multiple locations).

Sincere thanks for any guidance!

To avoid heat in June and July, consider destinations in the southern hemisphere, such as South Africa and Namibia, or certain regions in South America. Much of Asia will be hot, except in some mountainous areas.
I recently spent four weeks traveling in Japan and did not find it incredibly pricey, especially since the yen has dropped significantly in value relative to the U.S. dollar and other currencies. It's now less expensive to travel in Japan than it is in the United States and some regions in Europe. However, Japan will be busy in 2025, especially with this major event in Osaka from mid-April to mid-October: https://www.expo2025.or.jp/en/
If Expo is of interest, also visit Koyasan, near Osaka. It's the center of the Shingon sect of Buddhism and a UN World Heritage site. If you like the outdoors, check out Japan's many pilgrimage routes.
Hokkaido won't be as hot; and the spectacular flower fields around Furano will be in bloom.

You don't say where you are from, but I assume maybe Australia? As you don't list that as on option but places that would be easy to get to from there.

I don't know if you would consider Okinawa - it is sort of part of Japan. My daughter lived there for 3 years (courtesy of the US Air Froce, and my mom visited in June and she did not do hot weather very well. My daughter and her husband did a lot of scuba diving - if you didn't do that I understand the beaches are great and there is also snorkeling. IME places nearer the equator are warm year round but not exceedingly hot in the summer like places with seasons are.

I took my granddaughter on safari to Tanzania in June and it was quite surprisingly cool there at that time. We had great weather.