Hello, have a look at the suggested itineraries on this website :
https://www.japan-guide.com/e/e2400_tokyo_9.html (11 days).
How many people will there be in your group, exactly?
Regarding the weather, I personally found the heat and humidity terrible in July in Tokyo, and I believe it will be worse in Kyoto. Rainy days were a bit more bearable. If you have ever been to Singapore where it is hot all year round: summer in Japan is worse.
Now, 4 cities in 11 days leaves you with 2.5-3 days per city, which I think is a very ambitious plan for a large group with children. You did not mention the departure city, but if it is also Tokyo, I suggest:
- 2 nights in Tokyo
- 5 nights in Kyoto, with day trips to Hiroshima, Osaka, Nara
- 3 nights in Tokyo
Alternatively, if you arrive in Tokyo in the morning or early afternoon (roughly, before 3pm, so you can catch a train around 5pm):
- 5 nights in Kyoto (with day trips)
- 5 nights in Tokyo
Transportation (aka "should I buy a national JR pass?" (the answer is NO))
1) For the itineraries I suggested, the best option is to buy a round-trip ticket from Tokyo to Kyoto, and the Kansai Hiroshima train pass:
https://www.westjr.co.jp/global/en/ticket/pass/kansai_hiroshima/ (17,000 yens)
2) If you skip Hiroshima, then the Kansai mini pass is a much cheaper option
https://www.westjr.co.jp/global/en/ticket/pass/kansaimini/ (3,000 yens)
3) And if you want to replace Hiroshima by Himeji and are willing to take slower (=non shinkansen) trains:
https://www.westjr.co.jp/global/en/ticket/pass/kansai/ 4) get an IC card in Tokyo or Kyoto. In Kyoto you can get a special version that comes with discounts for foreign tourists (
https://kansaionepass.com/en/about.html). Apart from that, the only difference is the design. I find the ICOCA cuter than the SUICA :)
Other tips:
- Buy your (e-)sim cards in advance, one per adult, so that you can split and stay in contact
- For Kyoto, forget about buses. Stay near Kyoto station (for day trips), or a metro station (for easier access to Kyoto's attractions). I have never been in your situation, but looking at the map, Tofukuji station looks like a good option. Maybe someone else might have a better suggestion.
- Were you planning to visit Miyajima? Miyajima + Hiroshima is doable from Kyoto, but it will be a long and tiring day. Maaaaybe book a night on Miyajima if you really want to see it (in which case you should book a round trip from Tokyo to Hiroshima instead, with a stop in Kyoto. That exact same train trip has been discussed here:
https://www.japan-guide.com/forum/quereadisplay.html?0+179709)
- food: I love eel (unagi), it is a summer specialty, but some specialized restaurants will have a very, very, very long queue (outside, under the sun). Finding one in a department store should make the wait more bearable.