Traveling to Japan in March

Hi,

I have a few clients traveling to Japan March 20-27. They are intersted in getting the 7 day rail pass. Would this be the best option? they will travel from Tokyo to Nagano on 3/20, Nagano to kyoto on 3/22, and kyoto to osaka on 3/25, and finally osaka to hiroshima on 3/26. Would the 7 day rail pass cover bullet trains to all of these locations?

Also, does it require a separate visa to utilize the rail pass? Or will a travel visa automatically be issued upon entry to the country for US citizens?

Finally, how do seat requests work for the 7 day pass? it looks like it must be activated at a train station once in japan and then you can make seat reservations. Is it easier to book individual train tickets for specific days in advance to not have to hassle with this aspect upon entering the country?

Thanks,
Hannah Smith