My son and I are similarly landlocked in Oklahoma but have found local lakes to be a good way to get in cheap weekend dives.
There are two lakes in OK generally considered diveable.
Broken Bow is less than two hours from you. I haven't been there but I've been told there's at least one dive shop.
The other is
Lake Tenkiller, which is where we were certified and dive most summer weekends. It looks to be about 4 hours drive from you but there's camping available all around the lake and cabins for rent in the state park so you could make a cheap weekend out of it.
Conditions are typical for an inland lake. In the summer, surface temps are high 80s dropping down to about 70 under 70 feet or so. Visibility starts out sketchy in the spring (3-10') and gets better through the summer (better being relative but up to 20-30' in ideal conditions).
There's a dedicated dive park at the state park where several boats, a bus, plane, helicopter, and other smaller items have been sunk. There are at least two dive shops:
Gene's Aqua Pro and
Nautical Adventures. I've heard good things about Gene's but I trained with Tim Knight at Nautical Adventures so that's who we always use. He's got tanks, tank fills, wetsuits, and full kits for rent except for the basic necessities of mask, snorkel, and fins. From the limited info I've seen about pricing on the board here, he also has great prices on training and equipment. My son and I got full kits from him (Bare wetsuits, Atomic regs, & Zeagle Stiletto BCDs so not low-end stuff) for much less than I was able to price it on the web.
Sounds like you and your father are following a similar path. We got OW certified for a family trip to Turks & Caicos a couple of years ago and then did AOW last year, finishing up with our first liveaboard trip last Sept. And speaking of history & wrecks, we're going on a trip to Truk Lagoon with Tim & others this Sept. It's been on my bucket list since the first time I saw photos of the wrecks there.
My son and I each live about 1.5 hours from Tenkiller so we generally just drive there on Saturday, do 2-3 dives, and then return. You and your dad are welcome to join us sometime.