Southern California is very wide spread. Most basic services are available everywhere but they are NOT within walking distance when compare to NYC.
Are you moving to LA for work? Will you have a car? Who will care for your 7yr old (child care or at home)? Do you like the beach or the mountains? The answers to these questions will help you to determine your options.
Orange County is newer and it is more family oriented (Soccer moms atmosphere) The employer base are mainly technology industry , some manufacturing and health care services.
Los Angeles is a very large county. Movie/film, financial, medical research industries Children friendly cites include the West side - Santa Monica, Brentwood, West Hollywood, Marina Del Rey, Huntington Beach, Manhanttan, etc. The East side - Los Feliz, N. Hollywood, Silver Lake, Pasadena. North of LA county - Santa Clarita. NW of LA County - Woodland Hills, Agoura Hills, Sherman Oaks.
I hope the information helps.