School with multiple buildings: multipolygon?

I am currently working on mapping a city school that has various buildings. The buildings are spread around a few streets and have other unrelated buildings (e.g. houses and shops) and public roads in between them, so I can't just draw an area around the buildings and tag it. I have mapped out the buildings - sometimes using closed ways and sometimes using multipolygons for adjoining buildings - and tagged them as building=school. Some of these buildings have specific names e.g. Old Block, so I have tagged the closed way or multipolygon as, for example, name=Old Block.

Currently there is a node positioned at the school's reception to hold the amenity=school, address and website tags. However, this does not show exactly which buildings belong to this school, so I would like to use a multipolygon. (There is also another school nearby, with another set of buildings.)

I am using JOSM to edit. Should I create a new multipolygon for the entire school by selecting all the buildings (so that I have child multipolygons)? Or should I select all the outer ways for each set of adjoined buildings and use these to create a multipolygon? Or should I stick with what I have already?

If I go for a multipolygon approach, do I need to tag all the buildings with role=outer?

Thanks.