So I decided to make another save file of Mario Party 5

Strychnine said:
You have to play in party mode to get the minigames, and win those minigames IIRC. Aren't there a few settings that make Bowser spaces more popular? You can try to beat story mode to unlock Bowser's map and see if that helps.
You only need to play the mini-games to unlock them. There's an event in the last five turns where all red spaces are Bowser spaces, so that helps.