Well, if you're going to have a car and everything, have you considered VRBO? Sometimes, you can find a nice vacation rental that's cheaper and nicer than a hotel. But, then you'd have to pay for parking at
Disneyland every day you're there.
Close to Disneyland in October, less than $100 is going to be tough. October is more of a peak period than summer these days. I've heard Motel 6 Maingate isn't bad. It's Motel 6 though. If you can afford a bit more, like bumping it to $150 a night even if it means maybe doing 7 days instead of 10, there are quite a few more options.
I asked about the driving to Los Angeles before because most people don't realize how far away things are. Los Angeles is huge. And a lot of the activities tourists enjoy are nowhere near Disneyland. For instance, driving to and from Universal can be anywhere from 40 minutes to 90 minutes in traffic. If you want to see the Hollywood Walk of Fame, the wax museum, Ripley's, or other Hollywood attractions, you're looking at another hour drive day. Santa Monica Pier is a good hour or more depending on traffic, too. The part of L.A. that's close to Anaheim is...not the tourist part. It's the industrial wasteland, the not so great neighborhoods, the grittier parts. It's not horrible, but it's not like going to L.A. is a quick trip from Anaheim. If you spend a lot of time in southern California you already know this. But if you don't, it's something to consider, so I just wanted to put it out there for your awareness.