help and suggestions

Hello! We are a group of 2 families (13 pax) traveling to Fukuoka for the first time this December and staying for 10 days. Our stay will mostly be in Fukuoka but we plan to do a day trip each to Hiroshima and Nagasaki. Other than that, we intend to just explore Fukuoka. Our main requirement for train/subways will be from Fukuoka airport to Hakata station, trip to Hiroshima, trip to Nagasaki and most likely the trips nearby to explore. I am getting confused on what pass to get for a group of 13 with that itinerary in mind. If we get the JR Kyushu pass, will we be able to use it for our travel to Hiroshima and Nagasaki? If not, can you suggest what practical and cost sensible JR Pass to get with the given itinerary?