It all depends on what temperature you can provide.We are in CT. Can we keep 6 or less chicks safely in our garage with their heat (was thinking of the MHP) at the end of April?
They need one place that stays warm enough, even in the coldest temperatures. You could set up the MHP and check with a thermometer, to see whether it does stay warm enough.
Beyond that, it is nice if their water does not freeze, but chicks can run around even in below-freezing temperatures without trouble, as long as they are always free to warm up again when they feel the need.
Chicks can be kept anywhere that can provide the right conditions, and many times a heat source in a garage can do that.
If the chicks are being shipped to you, it might be good to keep them inside for a few days, so it is easier to watch them and be sure they have recovered from shipping. But I would probably move them out to the garage after that, or even to the outdoor coop if you can provide the right conditions there.I could keep them inside for a few days.