My mini list of things to make life easier:
Make a master list of all the clothes and accessories you want to bring. Write down every little thing from socks to swimsuits. Maybe even laminate this. DO NOT leave home without checking everything off of this list.
Take all food and drinks for the trip, to save money and time. Homemade sandwiches, chips, sodas and juices. A Nalgene of water for each person. Snack crackers, string cheese, fruit, and baby crackers.
Hotel reservation at halfway point. Preferably with pool.
Blankets, Pillows, Loveys, baby sling.
Books and magazines for everyone. Toys that don't make noise for the little ones.
Electronics and their chargers
And don't forget the hats and suncreen!