first off, you're lucky to have your grandfather's guns. keep them and take care of them.
second off, the .30 carbine, 12ga, and .380 are centerfire, the .22s are rimfire. both will fire .22lr, one will also fire shorts and longs, but those cost more, so you're set with a box of 22lr. if you go ammo shopping, telling the clerk you need .30 carbine, 12 gauge (bird or buck or slugs, depending on what you want to do), 380, and 22lr will get you the right stuff. personally, i'd skip everything but the 22lr till you're sure you're up to speed.
third, you haven't explicitly said how long it's been since you've been shooting, but you may want to consider looking around for nra basic rifles, basic pistols, and basic shotguns courses, just to make sure you're 100% on safety. or, check in the rally point forum and see if there's anything going on in your area. certain parts of the country are crawling with friendly high roaders who would be happy to help you out.
oh, and fourth: have fun shooting them!