Is there a way to grow peonies and lilacs in Northern California?

You can definitely grow peonies in Northern California. The best planting time is November to early February. There are some helpful tips here:

crickethillgarden.wordpress.com/2013/01/17/growing-peonies-in-usda-zones-8-and-9/

Yes you can. Check out this for step by step instructions. http://www.gardenguides.com/111349-grow-peonies-california.html

I'm a Minnesota transplant. Peonies do beautifully there and grow like weeds that bloom for Memorial day. Here in Northern Ca. we don't have enough winter cold . Plant the tubers shallowly with a scant covering of soil to take advantage of the winter cold that we do have. Some folks have been known to dump a tray of ice cubes in the winter for good measure. Tree peonies, do beautifully here however without any special treatments.