I agree 100% with Dreadylocks. You will definitely need signed releases from all of the above! You are also likely going to need to obtain a permit to film at the park since it is city owned. Also, the Catholic diocese can be very tough on releases, especially when it comes to documentaries...
Another item to keep in mind as respects to vintage production equipment is insurance. Most Production equipment insurance policies are written on ‘Actual Cash Value’. That means it covers the replacement value of the equipment minus depreciation, which includes obsolescence (loss of usefulness...
Also be advised, San Diego has a $2mm Liability insurance requirement in order to obtain the film permit. That requires a certificate of insurance be issued naming both the city and the county of San Diego as additional insured.
also keep in mind if you four-wall a theatre, aside from the costs to rent the theatre, almost all venues will require that you have insurance for the event/screening. That can add $250 on up.