Tammy,
You will be a much happier mommy and daddy if you vacation alone once in a while. DH & I crusied last July with 3 other couples on a 7 day eastern. We all left our collective 8 kids at home. (Ages ranged from 2 yrs - 11 yrs). It was wonderful!!!! DD is still pi$$ed at us for doing it but she understands that mommy and daddy need/deserve extended mommy daddy time. (What she doesn't know is she is going on a 7 day western in Dec with us and another huge group of people!

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Prepare to deal with disappopinted, disillusioned, MAD kids. But, they need to learn that mommy and daddy are the boss and they can do this and it is okay. Kids need to learn the world does NOT revolve around them. Promise to bring them back goodies and arrange for them to stay with a fun grandparent or friend and it helps take the sting out of the blow.
When we were gone DD spent a couple days with one of her best friends, and the rest of the time with her "spoil you rotten" DGM

DD got to go shopping, get a pedicure and manicure and other fun stuff. She didn't suffer too much! We called her from St. Thomas since we had cell coverage there and bought her lots of goddies from everywhere and took lots of pictures.
I had to laugh, DD's friend's mom is also a good friend to me, and boy did she tell on DD! Apparently they were going somewhere in the car and out of the blue, DD said "Mommy and daddy don't love me, otherwise they would have taken me on the cruise too!" My friend said she nearly wrecked the car to respond! She whipped around and said, "Kathryn! You are one the the most loved kids I have ever known! Your parents adore you! How DARE you accuse them of NOT loving you! They are taking this vacation to make them better parents! Don't you ever say ANYTHING like that again!" Gotta love friends like that!!!

Properly chastised DD said, "yes ma'm"
So do not feel guilty or bad about going by yourselves...it will only help you be better parents by remembering to be spouses.
Enjoy ALL the adult only areas, pool, Palo's, spa, Serenity Bay, after hours parties in the clubs, excursions YOU want to take...etc.
Enjoy and let us know what/when ya'll go!