I got married in November as well, and had the same concerns as you. I looked into the DR, b/c I heard it was cost-efficient and Puerto Rico and Cancun. My final decision was Isla Mujeres, about seven miles off of cancun. Finding this island was life luck.. it was perfect. Do you know how I found it? I literally typed in google, "small remote island off of _____ easy to get to by ferry." The google words worked for me, maybe they can work for you!
And plane tickets to my Nov 1 wedding were pretty reasonable, average was 320$ USD from D.C. including taxes, roundtrip to cancun.