I'm biased, as a fan of party games / minigame collections myself, but I remember enjoying my time with Game Day as a kid. The minigames are all good, and I really enjoyed exploring the island in 3D, with my only criticism for it being the monotony of the campaign. But overall it's a good game with some nice Club Penguin charm.

I also got a good few virtual coins off this game, as I played it back when Club Penguin's servers were still live and the coin transfer functionality worked, so I'm probably very biased.