Can the dough be frozen if I don't want to cook all three at once? If so, at what stage can I freeze them?

My experience with bread is that yes, unbaked dough can be frozen. The time to do that is after the first rise. Punch the dough down, wrap well, place in double freezer bags and freeze. You could divide the punched down dough into loaves before freezing, too. Be sure to defrost completely (in the fridge) and then form the loaf(ves) and let it complete the second rise before baking.