My first 4th in Irvine.
Please let me know where the happening spots to be are (family fun, fireworks, etc) in and around town, or where to look for such information.
In Irvine, there are two (I think there are just two) fireworks shows, Woodbridge South Lake and Northwood/El Camino (I forgot what park they fire them from... Heritage?).
The second one is at the very back of Heritage Park sponsored by the Irvine Police department. You can pay admission to go inside and enjoy other activities and sit close to the fireworks. Or you can sit at the Heritage Park and enjoy the free show. I live very close to the Heritage Park and will miss the convenience. People usually park in front of my house to walk to the Heritage Park.
If you're willing to drive about 15 minutes down to Rancho Santa Margarita (92688) there is a great firework show there at the Santa Margarita Lake - admission is free, though you will want to go there and get a spot early and put your mat down (people come early and have a picnic before the firework show that I believe starts around 9). The firework show is great!