Becky, your description sounds right on the mark! I participated in a couple of Garden Round Robins on DG and it was great fun! There were a few times where some participants didn't pack breakables securely and a few things did get broken during the travels but when we found something broken we just removed it, took out the item(s) we wanted and replaced with item(s) of equal or greater value. If someone had "extras" they would add them to the box as well. There were all sorts of things in the RR Box ... from packets of seeds, kitchen towels, bird houses, wind chimes, garden tools, little pots, hand made garden signs, little ceramic pot sitter critters etc.
How the Round Robin worked was the Host/Hostess collected all names/addresses of participants through d-mail, typed up a list of the participants names/addresses putting herself last on the list. Hostess packs the original/start box with a bunch of goodies and places the name/address list in the box and ships to the first person on the list. The first recipient takes out what she wants, adds item(s), marks her name off the list and sends the box on to the next person in line and so on. The last person who gets the box removes/replaces items, then sends it back to the hostess. Everyone just needs to remember to replace the name/address list in the box before mailing it!
Postage has gotten so expensive. If you use a regular box the postage amount will vary depending on the weight of the box as each person removes/replaces items. It would result in some folks paying more for postage. You might want to consider one of the Flat Rate postal boxes, medium or large (which isn't all that large). That way each person would be paying the same exact amount for shipping, making it fair for all. Postage for the Small Flat Rate Box is $10.95, Medium Flat Rate $10.95 and Large Flat Rate is $14.95.
I'm not joining in on this one ... too much going on this summer but I know y'all will have a ball. It's always so exciting, waiting and wondering what goodies you will find when you open the box!