Oak Glen is a nice municipal park located in Howell NJ. It contains numerous recreational areas. These include basketball courts, soccer, baseball and football fields.
There is also a large hill between the library and police station (across Old Tavern Rd) that is commonly used for sledding in the winter. Park in the library or at the top of the hill for easy access.
I have not been able to find any information on the 2010 fireworks. It looks like there might not be "4th of July" specific performance this year. Howell Day will take place on Saturday, July 10th from noon until 5pm. FOr more information, please this pdf, or this blog post (written by Bruce Kunz).