He could convert his amex points to continental. Redeem that for one F award and his UA miles for the other F award.

I would make sure you want to go to the caribbean. Hot, muggy, rainy and chance of hurricanes. Really not the ideal season to go.

I suggest Hawaii.

We had a destination wedding in July and had to eliminate everywhere in the caribbean due to bad weather. We were just not willing to chance it.

We ended up doing it in Cabo which is dry. It is hot during the day though. Cabo worked best for our needs, but I would think Hawaii is the best western hemisphere honeymoon in July.