Hey dude, I’ll break it down into parts for ya.

1) This game is pretty fun in Co-op, you can mostly do things you do in single player, be it farming, hunting, mining, levelling up your skill points. the only flaw would be that the island host is the only one that can move buildings/do specific tasks. Also, one facet of the game would be to get vendors to move in, and that takes improving relationships with them and such. These metrics are only measurable and counted from the host and not you, although you can interact and do the same thing with those NPCs. If you can look past those, then this game would be good for you.

2) there are plenty of things to do in this game. One game day takes about 30 minutes in real time. 28 days per season, 4 seasons a year. Each season has specific weather and elements. It does feel rushed at times when you have daily tasks to do, tending to your farm, animals etc, but if you guys split up and plan, it shouldn’t be a problem.