That's a tough one. We're from Lake Forest Park, have three kids (7,4,4), and have been married a year longer. So I think I can empathize fairly well.
I don't how long you're staying. We're going a week before you and staying seven days. I definitely didn't want to do LAX, so we did SNA. We're taking a cab, but I checked into a limo because I heard it was only slightly more. But the limo companies seemed a little shady and I was looking for piece of mind. The shuttle was out because it was more expensive for 5.
The nice thing about the car rental is that you control the action and the pace. We'll have access to a car because my sister is also going to DL from Vegas. That's good because we want to go to Costco for water, snacks, etc. There is also the Disney Character Warehouse store which is a lot cheaper (so I've heard) than anything at DLR. So the car might help you there if you have the time. So the car could save you a little more possibly.
On the other hand, who wants to drive in LA traffic, especially when you come from Washington where people are courteous and sane.
Like I said, it's a tough call. Good Luck.