I would recommend not renting a car. You won't need one for that length of time and you can avoid rental, gas, and parking fees (both hotel and parks) if you don't get one. It's very easy and pretty inexpensive to get from LAX, SNA, or LGB to
Disneyland. Stay on Harbor, across from the parks, and you'll just be walking across the street to get into the resort. From LAX, I prefer to take the bus. Google for a coupon and it's pretty cheap (Disneyland Express). From LGB or SNA, take a taxi. It'll be between $40 and $45 each way plus tip. You could also take a shared shuttle (I use SuperShuttle) for $11 each one way ($33 total each way for your party + tip), but I'd just go ahead and get a taxi since you can hop in and go directly to your hotel rather than dropping others off on the way. With only 3 people you won't need a dedicated shuttle and they're a lot pricier than a taxi.
I like Carousel Inn, Howard Johnson (Hojo), and Fairfield Inn. Other very popular motels in the same area are Park Vue Inn, Tropicana, Best Western Park Place Inn (very closest you can get), and Candy Cane Inn (they have their own dedicated shuttle), but I haven't stayed in those myself. I would absolutely avoid parking at DLR if possible! You'll waste a lot of time and money doing that.
Disneyland is expensive. I imagine WDW is too, but I'm not familiar with it. The motels above will run you roughly what you budgeted, maybe less if you keep your eyes open. I can usually get the Carousel for under $100/night. However, most of the area hotels/motels add a fairly hefty parking fee if you have a car, and some add a "resort" fee even though you don't really get anything for that. Hojo gives an AP or disboard discount, or they used to anyway.
I don't find DTD restaurants to be any cheaper than those in the parks, but if you go off site you can do the regular fast food and chain restaurant stuff. In the parks, share meals or get a kids meal if you're not a big eater. Try the wharf area in California Adventure or go over to Goofy's Sky School area and you'll see a big area with many different types of food. In Disneyland, there are garlic cheese bagel twists that make a meal for me over in the Princess Fantasy Faire area. I like the kids meal at Hungry Bear (small cheeseburger, fries, apple slices and a drink for $6.99). Jolly Holiday has great sandwiches for around $10 which I have to share since they're big. At most places, my 2 friends and I order a couple of meals and share everything. Trader Sam's at Disneyland Hotel is a great spot for that (and then you can splurge on a fancy drink).
Hope you have a great time!