Firstly, I set up a grid of nodes and performed a breadth-first-search (BFS) between a random node on the first and last row of the grid.
As the BFS adds new nodes to the path, each node is assigned a random minigame (the coloured nodes represent the minigame rooms).

I then had the grid manager spawn minigame rooms on each path node as well as walls on each of the path's neighbour nodes.
A start room and a finish room is spawned on the first and last node in the path respectively.

Lastly, I created four different minigame rooms (which all inherit from a base minigame room) and set each path node to spawn a random room at its location.
The number of nodes spawned in the grid changes based on what difficulty the player selects.