In your cooler months you can grow lettuces, which are ridiculously easy and rewarding, but once it comes summer you'll need crops that are more heat resistant. Radishes come to mind (and your daughter will love them - they take a month from planting to harvest), as do carrots, beets, and chard (all of which are low maintenance, plant and forget until harvest type things. They can all be started now.) A small patch of potatoes might be an idea as well - I remember being completely enthralled by digging potatoes with my grandfather when I was about 3 or 4 years old.
You can also plant annual fruit - strawberries are a great one since you can get them as bedding plants, which makes putting them in very easy. What's the shrub at the back of the yard? And the tree? (If you don't know, you can post us closeups in the Plant ID forums and we'll tell you) You may already have some perennial fruit production going on back there.
On the flowers side of things, maybe look for Marigolds and Calendulas, which are bright sunny flowers with very few issues, and if your daughter eats them there's no problem. Ditto to Pansies, Cornflowers, and if your yard is sunny enough, Sunflowers (they die in the shade, but if you've got a full sun spot that would roast other plants, sunflowers will thrive in it.)
If you want something a little more permanent but still very easy to grow and care for, check out 'Dwarf Orinoco' and 'Dwarf Cavendish' (or if you're very lucky at the nurseries, 'Dwarf Red') banana plants (they should be appearing in the nurseries around now). In SoCal, you'll see edible fruit in about a year and a half; the plants themselves are very beautiful, and grow quickly.
For cherry tomatoes, the very best ones I've ever grown and eaten (and I grow anything between 4 and 40 types a year, depending on space) have been Sweet 100 and Sweet Millions, followed closely by Strawberry. You'll need a cage or similar type of support, because these are vining plants and if you let them lie on the ground, the bugs will eat more of your tomatoes than you do. Sweet 100s are particularly problem-free plants; you shouldn't need more than 2 or 3 vines total to supply you with tomatoes throughout the season. If you're starting from seeds, start now; if you're starting with bedding plants you've got a bit of time to look for them.
Aaaand, probably I should have started with this, but take a look at your soils before you plant anything. If they're very crumbly or anything less than a rich brown or black when moist (ie if they're grey or reddish) you should think about getting some compost or hummus and turning that in before planting. Sniff a handfull too - good soil has no chemical smells, just a deep earthy fragrance which is quite pleasant.
Now that I've written you a small novel, I hope it's helpful! Happy Gardening!