Hi, I'm a small wholesale grower and I might be able to help. What I use is just regular bark dust that you can get in the truck load and then I use a slow release fertilizer, such as osmocote. They sell a fair sized container at home depot for about $10 that would work for your maples.
If you're getting them in the mail and they're one gallons then they're probably fairly young grafts. You could put them in the ground if you know where you want them and they would need lots of water through out the summer.
If you want to keep them in containers then you'll need to fertilize them and be sure they don't dry out.
Maples like a little acid, so if you're a coffee drinker you might throw your grounds in their growing medium also.
It doesn't matter all that much what you put them in just so long as it's not a 2 way type variety, or dirt out of the yard. That kind of dirt gets really hard and makes it so the roots don't get any air. That's why we use a really course bark type medium. Another thing with potting soil and peat moss is that when it dries out it's really hard to get it to be wet again.
Good luck with your trees!

Thanks, jcmaple. I'm a small grower (ormanental grasses) as well, but this is my first attempt at Japanese Maples.

I have a wide selection of large containers, up to ~25 gallons, and I make my own mixes, so I'll be able to give them good homes and media. I'll add a little Holly-Tone to the mix for the acidity. The basic "Al's Mix' is 3 cubic feet of pine bark fines, and 5 gallons each of perlite and screened peat. I usually use compost and compost/Eelgrass tea for ferts.

The trees shipped on Monday, so I'm hoping they arrive before the weekend.

I have three babies all in pots. I use Tree and Shrub soil and they seem to like it. I also use a little Osmocote as well, so far, so good.

They just arrived.

They all appear healthy, although the 'Bloodgoods' have some tatty leaves.

The 6 dissectums are fairly small, 1-foot tops grafted onto ~18" stems. The 'Bloodgoods' are 2-3' tops grafted onto 4-6" stumps.

The packing slip lists OH as the point of origin. Anyone know who in Ohio is doing Japanese Maple grafts?