Will I be able to enjoyably play Untitled Goose Game on a 13” MacBook Pro, especially given that I don’t have a mouse, and no external keyboard? Or are there some controls that either require the mouse or else are too cumbersome to do without a mouse (ie with just keys)?
The official support page for the game states:
You'll need two controllers. On computers, a mouse and keyboard counts as a controller, so you can play two-player with that, plus a second non-keyboard controller. On Switch, you can control your goose with a single Joy-Con, so you can play two-player with a pair of Joy-Cons.
While you will have your keyboard and trackpad, I imagine that will be quite difficult. Trackpads are usually never a good choice for playing games on a laptop/computer.
A Reddit post also claims:
Using a laptop/tack pad is pretty difficult with this game.
The actual input is difficult, but the camera moving around and shifting means that you'll often not actually click where you clicked.
Thus, you probably won't be able to really enjoyably play this without a dedicate mouse at the minimum. You could probably use your laptop keyboard with a separate mouse fine though.