18 Days Family Travel

Hello There,

I'm preparing our family travel to the wonderful Japan. W're 4 People ( 2 adults and 2 kids 3Yrs and 5Yrs old) and planning to make a trip in Japan.
Our itinerary is next: Arrive in Tokyo (stay 4 or 5 days)
Tokyo -> Kyoto ( also 4 or 5 days)
Kyoto -> Osaka (4 days)
Nara ( wanna make a stop in Nara for a night in temple. Not sure if better to do before Osaka or after)
Osaka -> Hiroshima
Hiroshima back to Osaka.

I'm open for any request or tips.
My main questions is to know what Pass to take. The price of the JR pass cost us a 1026 €. I've seen the Kansai-Hiro area pass or the Osaka-TOkyo arch pass.
Don't know if we can combinate different pass? What about the price for kids under 6 years?

Thanks for reading
Kindly
DOJI