Welcome to FT miniflies!
Overall, I'd recommend both you and hubby each getting whatever cards you find beneficial. That way you're both getting the signup bonus miles. My wife and I have really hauled in the miles that way which helps since there are 3 of us. Not to mention applying for the Business versions of the cards, too.
It sounds like the SPG Amex, BA Visa, and Citi AA card would be good fits based on what you've said. Just my opinion, but I would wait for a generous signup bonus before pulling the trigger. I usually won't apply if it's only 25K or 30K.
Citi AA just ended (I think) the 75K signup bonus but it's likely there will be something else coming along soon, if not already. Your husband most likely can't get another personal Citi AA card bonus but you certainly could. However a Business Citi AA card would work even for him.
BA currently has a 50K bonus offer, I believe, not as big as the 100K offer they had a year ago but still nice. We like that the BA card earns 1.25milkes/dollar. We got the SPG (Starwood) Amex last year with their 30K offer, but I think their standard is 25K (part of which requires a minimum spend). Still use the SPG Amex a lot since it's so flexible and has the 5K bonus per 20K miles transferred to airline miles.
I'm not familiar with JetBlue or Korean. But with these or any of the above, just do a few quick searches here in MilesBuzz and the relevant airline/SPG forums for the latest news and offers.
Good luck and happy travels!