We’d say it’s about a 20 minute walk from your campsite to the nearest beach access.
As others have mentioned, turn right out of the RV park and then left onto the sidewalk that follows the street under Hwy. 101 (no need to cross the highway). Follow that straight west into town. At the crosswalk across from Pelican Brewing, go straight. Walk along the path just north of the Hallmark Resort’s cute dog park. At the west end of the park, the path turns right onto a grassy right-of-way that becomes an alley. Take the first left onto a footpath and you’ll be at the beach in one block.
We love this walk.
If it’s too far for your littles, consider driving to the Pelican/Hallmark intersection, turning right, and turning left onto Washington and parking along the street. Easy beach access from there along Ocean St.