Advice for Large Family Accommodations

Hello everyone, new here and planning our first trip to Japan. Fortunately for me I've been promoted to general planner for this trip so I'm starting with accommodations. Now I know it's largely frowned upon in this sub to support and use Airbnb for booking but so far it's been the easiest for finding accommodation that fit our budget and sleeping arrangements.

For reference we have two families of 4, my children are 15M and 26F, my sisters children are 7 and 11. My mother will also be with us so an extra body to add.

Would anyone be able to recommend a better way to book something that fits our family? Thanks in advance.

by AlbertaSparky