As others have said, there are some things which cost extra and, obviously, the food is not included but the majority of rides, games etc. are included with the entrance fee.
I have read various reports about Disney Quest on here. Some like it and some don't. For us, we had to spend a whole day at DTD last September while waiting for our airport pick-up and went to DQ. We left for a couple of hours to go to the pictures but mostly spent about 5 hours there. There is plenty to do and, when we were there, there were hardly any queues for anything although I believe it can busy when it's raining and at weekends.