Grownups

Here are some activities that really don't work well with younger kids.  Older children would probably be okay, or just save these for your date night:

Sycamore Mineral Springs, Avila Beach.  On the side of an oak covered hill, Sycamore Mineral Springs Resort has private hot tubs that you can rent that are supplied from natural hot springs.  Very relaxing and/or romantic.  You should probably reserve ahead of time if you want a weekend evening in the summer.  Otherwise, you can usually show up and they will have something available.

Crux Climbing Gym, San Luis Obispo.  Although there are several climbing spots in nature around here, if you don't have your own gear, or don't trust your buddy, Crux Climbing Gym is a fun place to go and climb.  If you haven't gone ever or for over a year, you will have to pay to watch a safety video before you climb. 

Oceano Sand Dunes.  It is unreal to me that this crazy fun place still exists.  So go before you can't.  You can take Off-Highway Vehicles out on the dunes and do whatever you want.  Crazy, huh?  There are several places down there to rent from, all are expensive.  But how cool.