Soufflé the day before?
The problem is that you want the soufflé ingredients to be room-temperature or above when you put them in the oven, so the soufflé will puff up. But this sweet-potato mixture would have to be refrigerated if you make it in advance (especially because it contains eggs), so that won't work well.

Here's what I would try. (You should check with your hosts to see if they have room in their kitchen and oven to do this). Make the topping in advance. Bake the sweet potatoes in advance. Take the other ingredients with you, allowing them to come up to room temperature. When you arrive, microwave the potatoes to reheat them, beat in the other ingredients, and bake.

Or bake the soufflé at home just before you leave, letting it rest before you transport it. It will be completely collapsed when you serve it, but it will still taste just as good.