Since you have not flown for quite a while, I would suggest you go to Delta's website to familiarize yourself with their baggage policies (size, weight, etc) and then read up on the whole liquids thing, etc going through Security. Please note that it is a good idea to watch those going through Security before you to see what they do. You will see that all jackets, sweatshirts, etc need to be taken off and put in a bin. You will also need to take off shoes. When boarding the plane, they like everyone to hold their own boarding pass ... unless your children are toddlers or infants, be prepared for your children to hold their own boarding passes when they are called.
Additionally, many airlines do not pre-board families with small children for the Orlando flights ... because there are so many.
Anything you can do to update yourself on airline, Security, etc practices will help you feel less stressed along the way.
A good money saver re beverages ... take an empty water bottle or two through Security and then fill it up at the drinking fountain. I do this all the time and then don't have to 1) wait in line to purchase water or 2) pay the huge price for a bottle of water to take on the plane.
Anything you think you may need access to on the plane should be in a backpack/bag that you store under your seat. So many times I see people board and THEN try to pull out the snacks, books, iPods, etc ... thus holding up the boarding process.
You will feel just like one of a herd of cattle, but that is the reality of flying these days. Just do your research, keep your eyes open, be prepared, and you will be just fine.