We went to Mexico when our daughter was 11 months. Not only was I 5 hours away by air, but I as in another country! But I knew we had left her in good hands, that she recognized and loved her babysitter, and that me and my hubby needed the couple time without the distraction of kids.
It's important that you leave a notarized medical authorization form for the caregivers, just in case something happens and they need to go to the ER. (I probably set you off worrying with that comment... Sorry. Don't worry, nothing will happen!) Message me and we can trade email addresses if you want a copy the forms I use. (At a previous job, I signed up for the $10 a month legal benefits; so I downloaded those forms...)
You'll also want to have a notarized document that you and your husband sign which says who you appoint as guardian for the children in the event both of your and your husband's "untimely death".
By the way, the first trip away was emotionally hard... By the 3rd trip, you'll be counting down to when you get on the plane! (Have fun!)