I'm sure someone will move this but here's an answer to get started in the meantime.
There are rides for just about every age able to comprehend the world. For young kids most will be in toon town and fantasy land. Depending on just how young the kids are and how easily they frighten you may want to scope out some of the fantasy land rides like Mr. Toad's Wild Ride as it's a bit dark (in the theatrical sense) and moves fairly fast. Still, kids tend to love this section of the park.
This time of year there will also be a few shows on the weekend in both California Adventure and the main park. Rides like startours are a must do for boys over 4 or 5 and small world for girls of any age. The new nemo ride is now open and kids do love nemo, the line however can be unforgiving.
Besides rides there's the obligatory over priced meal. For better food or healthier food try the space cafe in tomorrow land (near the starwars theater) or the pavilion just past main street on the road to fantasy land. If the kids are old enough they may enjoy the starwars theatre which is interactive with kids getting light sabers and the whole 9 yards.
You can also take photos with the cast characters, some will be wandering the park, others will be in set seating areas with lines. There's a plethora of shops to waste money on those "must have items" and lots of junk food to consume from any of the dozens of snack shops. It's all a part of the Disney experience and makes for more photos. Be sure to bring spare batteries and memory cards, neither are cheap in the park.
If you're going in the next few weeks you'll find the park is all done up for Halloween, which is rather fun and something that many people don't see. There are a few rides altered for this like the haunted mansion but younger kids may not do too well on that. After that they switch to Christmas theme which is also fun with fake snow and lots of other extras.
If you plan to stay all day bring or rent a stroller if the kids are still in that age. Disneyland isn't the size of disneyworld by a long shot but it's big enough that I feel it after a full day and just about every time I go (season pass holder) I watch some poor father or mother trying to carry their kid from the very back to the very front.
There's a calendar of events which you may also want to check out that lists each day's special events.
http://disneyland.disney.go.com/disn...&date=20070928
Have fun and remember, the best way to enjoy the park is to make sure you get to enjoy it too.