You actually picked one of the best times to go to Yellowstone. End of season (after Labor Day) is the other. That is a good time, because everything is still open for a few weeks but the crowds drop dramatically and the staff are relaxed after a hard summer...and everything is on sale in the stores.
This time of year you get to see spring in Yellowstone and that can be beautiful. You were extremely lucky to see momma bear and cubs. Remember it. People go for years and don't see something like that.
Here in a week it begins and there will be 5 to 10 times as many people as when you were there. As soon as the kids are out of school it starts... Watch the rental RV's carefully...