If you need to cool off, Phil Rizzuto Park in Elizabeth is a playground with a fountain and is bustling with activity. This playground has swings, plenty of climbing equipment as well as a ballfield nearby. Feel free to wear sandals, since this park has no wood chips. This park does get extremely busy in the warm summer months, so you may want to go during off-peak hours.
Make a Day of It: This park also is part of Union NJ. If you want to stop for a family friendly meal, get one of the best hot dogs in the area, by visiting the Galloping Grill on Chestnut Street.