Hi, welcome to the forum.
I am the web master and will be happy to answer any specific questions you have about relocating to Costa Rica or Panama. I don't have any interest in any of the properties for sale on the site. That doesn't mean I don't want you to buy one though!
You will definitely find that real estate is cheaper here than in California. The cost of living for most day to day items is less too. Although appliances, certain furniture, and other items can be more expensive here.
If your grandkids are school age, you will find good private schools from $150 per month to $1500. Some schools are on the US academic calendar (September - May) and classes are in English only. Other schools are bilingual and the majority are on the Costa Rican calendar (February - December).