Gigglin Marlin is a good shop, as far as I know. I've only been there once, when
@Cthulhu Calls (my partner) did his discover scuba there. I was actually impressed with the amount of instruction that he got. I expected them to just throw him in the water with gear and some basic instructions, but they went into a lot more detail than I expected. And
@VanessaArrrr used them exclusively for a long time, although I'm not sure if she has taken any classes with them. She could definitely tell you more about them. I'm not sure how often she hops on the board these days, but your best bet would probably be to send her a direct message.
For SSI/PADI, have you checked to see if you could use Gulf Coast Scuba for your VA stuff? Carl and Aiar are both excellent instructors.
@Cthulhu Calls took his OW through Gulf Coast, and Carl was his instructor. Plus Carl has been teaching in Houston for like 20 years or something. And
@SilverBubbles did rescue and rebreather classes with Aiar, and she always spoke very highly of him.
RE: taking AOW in Houston ... the main reason I would advise against taking it here is the deep dive. There's only one place around here to get your deep dive done, and that's at Mammoth Lake in Deep Hole. Which is literally just a 60 ft hole in the lake, in pitch black, low viz water. The other option is Lake Travis in Austin, but it's going to be basically the same. I did my AOW in a lake in Oklahoma, and that deep dive was not a pleasant experience. To paraphrase my dive instructor from back then, the bottom of a lake is damn deep, damn dark, and damn cold. If I were you, I'd do it somewhere tropical, like Cozumel.