Just an FYI-Ridemax strongly recommends the single rider line. They say, and I have read here, that if SR is closed just come back a short time later and try again. They just close it when the SR line gets too long to give it a chance to shorten a little. With how long it takes to get a FP and how long the return lines are, they claim SR is the way to go. Now in the case of the OP that wouldn't work, since he has a 6 year old with him.
Also, for those of us with only a couple days in the parks, we have to weigh whether or not the wait is worth it. In our case, my son is almost 13. We want to see Carsland but if we don't get to ride, it won't ruin our trip. I can see how it would be a huge deal for someone with a 6 year old though.