Your story is similar to my first time with the blower. It had enough gas, but was an older model (1970ish) and was such a struggle to use. After one pass, and dragging it back up the driveway, I put it away! Our driveway now is alot bigger and hubby uses a 4-wheeler with a blower on it to clear it out. Just be very, very careful clearing out the blower if it gets stuck with ice and snow. A friend of ours thought his hand was out far enough when he pulled out a chunk of ice, but the blades spun around once the pressure from the ice was off, and he lost 2 of his fingers.
I forgot your son is still a little, little guy. Soon you'll be out there with him! My girls loved being pulled around in one of the baby sleds when they were little.