Also, you would want to ask if you need and want to be in title as parents, since to divest your title will cost money, or would you prefer just to be on the mortgage note. In either case, in order to relieve you from the re-payment obligation your son and daughter-in-law would have to close out the old mortgage loan. This is a bit messy and expensive.
As to ownership, if it were Texas, all would be tenants-in-common unless some other arrangement were specified. Your attorney in California can help you with what happens there.
So, consult someone in the area where the condo is going to be so that if you need help when there, the same lawyer can help you.
If I understand you correctly, it appears that you need a Co-borrowers agreement. This agreement has many advantages for both the parents and the daughter/fiancee. Feel free to contact me at your convenience to discuss your situation for the proper solution. My contact information is available on my web site.
Best to ya,