Unless you are in a remote area, you shouldn't have to order bearings. Any decent hardware store, automotive or machinery parts store, or even big box home improvement stores should have 3/16 and 1/4 loose bearings, they may or may not have several grades, but we are talking about a well used Huffy here, any grade bearing will do. Just pull the axle from the hub and use the magnet to fish out a bearing. Take it to the shop and get 20 of that size (this will give you a couple spares in case you drop one, those things disappear the instant they hit the floor.
If you need a new wheel, hit the bike co-op. The sad news is that Huffy and many other low-end department store bikes are designed to be disposable. The replacement or upgrade of any significant component can cost you as much as a new Huffy. If you can keep it on the road for the cost of grease, and occassional cables, brake pads and inner tubes, they can be functional transportation. As soon as you start having to replace major components or have a bike shop work on it, you will be throwing good money after bad. Being you already bought the Huffy's give them a shot. If you start putting more than a few bucks into them, I'd suggest cutting your losses and look for used brand name bikes. Older used steel-frame MTBs and even many old 10-speeds will be more reliable than the average used Huffy and should cost under $100 even in good condition.