Travelling with a Team of 12

Hi

We are travelling with a Team of 12 swimmers from New Zealand to compete in the Aquatics World Championships in Fukuoka. We want to buy a JR Pass to cover our travel from Fukuoka to Hiroshima on the 22nd July, and then from Hiroshima to Tokyo on the 23rd July, and then around Tokyo until the 26th when we will leave to come home to NZ. Are there any special arrangements for buying group JR Passes? Does it make sense to buy a 7 day JR Pass? It seems to only allow you to buy up to 6 JR Passes at a time. Do I just do that twice? And can we book train tickets straight away after we've bought the pass even though we won't activate it until we're there?