I have done the exact thing back in 1992 moving from Los Angeles to South O.C. Then my kids were same age as your . I had to call Dept. of Education and many other places to find a good school in south Orange County. I decided to move to Mission Viejo which I found one of the safest, cleanest cities in South O.C. It was and still is a perfect city for a young family. My both kids went to Del Cerro which offers the best GATE (Gifted and Talented Education ) program. There is Mission High which is Nationaly recognized. I lived and raised my family here in Mission Viejo. This is just my story. I found Aliso Viejo also nice for young families and has award winning schools too. You will get more for your money in Mission Viejo.The homes are larger with bigger lots. The communities in Mission Viejo are built in more specious settings. If you don't mind the older style homes, you will get better deals in Mission Viejo.
p.s. check out the Mission Viejo Library! One of the most expanded and modern Library in South County.
Good luck and all the best for your move
Mortgage and Real Estate Broker