Tip #1: Parents- Bring a camera
Tip #2: Moms & Dads- (and super involved grandparents: strollers are great for the little ones. I recommend a "jogging" stoller with larger wheels.
Most stollers are fine as long as the wheels are pretty big. A small "umbrella" stroller will not work. It gets stuck in the ground cover and you will be frustrated.
Tip #3: Early or late. I can not stress this enough. Although in May and parts of June the weather is great, the hotter it gets, the more important it is to keep the little ones out of the mid-day heat. If it is hot- come early or late and everybody will have more fun!!!
Tip #4: When its hot- wear a hat and put on sunscreen. Especially the little ones.