I wanted to know your route because you asked about a scenic place to stop and picnic. If you take the 101 route, I can't really think of any scenic spots along this route for a picnic, except Paso Robles wine country. But you would have already been on the road for several hours by then.
If you were to take the Hwy 1 route, I would recommend stopping in Pacific Grove (next to Monterey) and getting sandwiches to go from Goodies on Lighthouse and then driving down to Lover's Point Park for your picnic. Very beautiful spot.
Of course, there are other lovely places to stop along Hwy 1, such as Capitola or Aptos, but I'm not familiar enough with these towns to tell you where to stop.
Once you arrive in Cambria, you'll be treated to a small, but relaxing town for vacationing. You'll find lots of interesting shops and Cambria has some of this county's best restaurants. Robin's, Sow's Ear, Brambles & Black Cat Bistro are excellent. If you prefer something less formal, there's the Harmony Pasta Factory as well as two mexican eateries on either side of town. The Main St Grill is also popular.
Be sure to take a sunset walk along the boardwalk on Moonstone Beach drive.
For a nice hiking experience, drive down to Montana De Oro and walk along the bluff trail. It's not a "serious" hike, but you "lazy trail" gals will enjoy it. Montana De Oro is a few miles south of Morro Bay.
Other fun hikes would be north of Cambria on Hwy 1. Salmon Creek is a short hike to a waterfall. Big Sur & Point Lobos also have great hiking.