Two bedroom apartment or larger room that can accomodate all 5 in one room.
It depends on your budget and how is the quality about affordable itself.
If you’d like to save money try Asakusa, Ueno, Kita-Senjyu, Kinshi-Cho district, not Ginza, Shibuya, Roppongi and/or Shinjuku district.
There are tons of trifty hotel/ryokan for travelers over there.
If you wanna try to have some traditional experience rather than economy, how about this for example.
http://www.sadachiyo.co.jp/e/eindex.html
If you rather prefer economy price, here are some candidates too.
http://www.sakura-ryokan.com/english/ehome.html
http://www.ichi-fuji.jp/main2.htm (no meal service)