What a great idea for Christmas gifts.
Mason bees require a food source (early fruit trees, etc), a suitable place to nest, and a chemical free environment. They are very sensitive to chemicals.
Mason bees can be finicky and if they are not happy with the location, they will leave the area. They will thrive in one area, and be void in another.
I would, just as it's good advice for honey bees, get a book on masons. There are some paperback books that can be bought for 10 dollars or less.
Masons pollinate for a given timeframe, about 6 weeks, then are inactive the rest of the summer. You must protect them from predatory wasps after they complete there cycle. I mention this, because they do take some special care if you are to see them thrive and multiply.
I have no idea if masons live in the south.
And if you do make the homes out of wood, invest in the thin paper tubes that can be changed out and clean ones replaced.
Good luck and I'm sure you will love the world of masons.