4 AMEX cards simultaneously is a bit of a stretch, but not unheard of. Someone else can opine better on whether your credit scores are good enough to try (personally I wouldnt, but thats just me). You definitely can get 2 since you have a business as well.

Despite their cutbacks, Delta is definitely the right airline to be amassing miles with if CVG is your primary airport.

I would also consider the Hyatt Chase card (gives you 2 free nights), and if your wife gets it too, thats 4 nights free. Hyatt's properties in Hawaii are pretty good IMO, particularly Kauai.... one of the best.

You could get BofA Hawaiian Airlines cards for easy intra-island flights.