Building/designing and open world - Terraria is well worth the money. Couch (split screen) co-op, and people can do their own things and team up to take down the bosses.

Glympse is a possible app I’ve used for this in the past. You set a time in the app that you’d want to share for, and others can either view in an app - else they can watch via a unique web link on any platform.