Here's my stab at your response for what it's worth:
Hi Wife...
Yes, the girls and I will be gone during that time as our reservations have been made. I think I understand how you are feeling, as I sure miss the girls as well when we're apart. I do think it's important for us to maintain normal activities, like family trips, etc. for the girls' sake and though it's not the ideal way we'd like to spend the vacation, I'm looking forward to getting away.
I have a couple ideas as far as maintaining contact. Would it be helpful to you if we made it so you could see the girls while we are away? Web cams (skype... something like that) are easy to use and would give you the opportunity to talk to them "in person" each day. Of course, there is always e-mail, cell phones and texting whenever you want to say hello! I am open to other suggestions but I do need to proceed with the plans I made some time ago. Thanks! Antlers