To get Bowser Land, complete the other 5 scenarios on the menu. Once you do that, Baby Bowser will kidnap Toad, and you will be able to play at Bowser Land.
Buy Mini Games
Do the following and then Woody will let you buy Mini Games off him.
Unlockable
How to unlock
Buy Battle Mini Games
Clear Mini Game Coaster on Hard
Buy Item Mini Games
Clear Mini Game Coaster on Normal Difficulty
Secret Minigames
1. Dungeon Dash
Complete the Mini-Game Coaster on Normal, then go to the Park (with the trees). A Pirhana Plant will give you this Desert Dash remake for here and the boards.
2. Rainbow Run
Buy EVERY Mini-Game (including Item and Battle ones) to get this Tightrope Wake remake from old Pirhaney.
3. Driver's Ed
Buy all the Mini-Games, then talk to Woody. He'll let you inside of him for this 1 player 5 level mini-game. Drive through the cones in the indicated order and direction.
Taunt
Hold down the 'L' button on your controller to taunt your opponents on their turn.
Unlock 1P Coaster
Play all the minigames in Adventure mode to unlock this. You can also then buy any minigame you have played at least once.
Unlock a new game type
Buy all the mini games that woody has. When you have bought all of them you will unlock the mini game stadium.
Unlock Credits Machine
Once you beat Bowser Land go to the Option Lab. There will be a Credits Machine to the right. You can use this to see who made the game, etc.
Unlockable
How to unlock
Credits Machine in Option Lab
Beat Bowser Land
Win Coins when using a Mushroom
If you use a Mushroom/Golden Mushroom, you can roll 2/3 dice blocks. If you get doubles (two of the same number) out of a Mushroom, Toad will give you a 10 coins present. If you get two 7s, Toad will give you a 20 coin present.
Using a Golden Mushroom is better too. If you role triples (three of the same number), Toad will give you a 20 coin present. If you get triple 7s, Toad will give you a 50 coin present! Very difficult to pull off.
Access Bowser Land...