Glad you started playing the game I recommended. When I was little my father and I played the two player mode of this a lot. We beat the game countless times. I think we decided it was best to stick to only the Machine and Spread guns. All the other weapons seemed gimmicky. The game still seems like a super neat cooperative two player game.
Awesome stuff, thanks for sharing your experience with playing the game with your Dad and for the suggestion. The Spread Gun is a nice choice as it covers a wide rage and can hit multiple targets.