Is there a fee to use the grill in picnic areas? Does it need to be reserved in advance?

There's just an entrance fee. No reservation needs.

Serena, There are drop-in (no reservation) picnic areas throughout the park and some have grills available. See the map at https://parks.smcgov.org/sites/parks.smcgov.org/files/HuddartMap-Nov2018-FINAL-web.pdf Please don't bring portable BBQs as those present fire hazards. Vincent is correct that there is a $6 entrance fee.

Fee to enter, no fee for grill. Group area reservation, first come on individual grill.