I've been to
Disneyland several times and always notice a few things that kids always love - and that give parents a break. I'll just give you my best.
1) As mentioned above - Tom Sawyer Island. There is so much to do and see here (small caves to walk through, bridges to climb across, interactive props, etc.). Best thing about it for parents? Its an Island - you can let the kids run loose and not worry about losing them. It isn't very big either - they would be able to hear your voice if you called for them.
2) There is a small "shooting range" (very interactive and cheap) right in Frontier Land next to the Pin Shop - $1 for about 3 minutes of shooting. Kids will be very occupied and you can relax while they have some fun or join in for some competition.
3) Pirates is a
great break from the action of the parks. It is an 8-10 minute long ride that loads very quickly (45 minute waits are usually about 20). Expect full blast air conditioning, water, and the dark to give you some rest while the kids are blown away by the ride, which is one of my favorites at any Disney park.
4) As mentioned above - Rider Switch passes be great for your family if you have children that don't meet height requirements. Most CM's at the fastpass entrances and ride exits will have them readily available - but this is what I always see people doing and its genius: Get a FP for a popular ride - ride it, and on the way out get your switch pass. This way you won't have to wait in line in the first place! Not against the rules either - just a smarter way to do things.
5) There is a really cool art gallery and shop right outside of the Hall of Presidents. It houses a lot of original memorabilia from Disney Lands early days like miniature models. The kids will love it.
6) Save California Adventures for a day where you have a lot of energy. In comparison to DL, it has far less places to relax and take a break. River ride breaks down often in the summer and there aren't many places for shade.
7) I'm sure you know this but incase you done - all the shops are interconnected down Main Street - if its crowded, just walk through all the shops for a quick route to the hub.
Fun things I always do to mess with my nieces/nephews: Pull the rope in the line for Indiana Jones even though it says not to, look for the queen peaking through the curtains in Fantasy Land about every minute or so, and tell them you were actually the one that put the sword into the rock in front of the carousel in Fantasy Land. Their reactions are always hilarious. There is also something like this on Indiana Jones in a long room with skulls on spikes, spikes coming out of the ceiling, and bamboo poles holding up the ceiling. One of the bamboo poles is bendy and bent a bit. If you grab it and yank on it there's a big rumbling noise and the ceiling starts dropping for a few inches. It'll be the pole with the sign that says do not touch. Its hysterical when you manage to catch someone off guard with it.
If any of the kids like Autopia - they can get a "license" made for them by the exit. It costs a few dollars but its worth it. I still have mine from when I was a kid.
The "I regret this decision list" for me: The rowing boats around TSI and riding either of the large boats in the river. Its exhausting.