K.T.
Hey I., I've been in Torrance for the last 15 years.
As far as local parks go, Columbia park (190th and Prairie in Torrance)is usually pretty good. It's very large.
You can get catering from El Pollo Loco or Togo's, both of which are very close by. I don't know about a jumper for a 3 yr old, but if you will be having older kids, they may enjoy it. THere is a bathroom, and a lot of playsets.
Another good one is 'Rocketship' park in South Torrance. It's up on the hill, close to PV, and has a lot of playsets, picnic areas and is usually a little less crowded. Amazing view of the South Bay too. Only drawback is it does get a little windy.
Another option, especially if you will be having a lot of kids, is Kids Concepts on Hawthorne in Torrance. They do the whole thing, pizza, cake, party room, and have a huge indoor play area. Chuck E Cheese is OK, but tends to be very crowded and noisy.
Hope that helps. Email me if you need any help... I've been to/done a lot of parties here.