Ahh I was looking at that the other day and was tempted, but perhaps wrongly dismissed it as I didn't enjoy the co-op in Monster Hunter World. Glad you're both having fun taking down monsters together!
Also on the co-op train currently: my partner bought It Takes Two so we've been going through the campaign little chunks at a time. The 'toy world' is beautiful, clever, and filled with mini-games to discover and compete against each other beyond the main puzzles and platforming. Not incredibly challenging, though it feels polished and has been a lot of fun so far.