I think you will find that most of the RV parks are already booked for the 4th. The best you could hope for is get on a waiting list and maybe someone cancels. The coast from San Francisco to Santa Cruz has the following parks:
- San Francisco RV Resort
700 Palmeto Ave
Pacifica
- Pillar Point RV Park (BEST but 1st come, 1st serve)
4000 Cabrillo Hwy
Half Moon Bay
- Half Moon Bay RV Park
460 Wavecrest Rd
HMB
- Pelican Point RV
1001 Miramontes Pt Rd
HMB
- Costanoa KOA (Pretty but east of hwy 1)
2001 Rossi Rd at Hwy 1
Pescadero