Dinky and Boomer weren't really necessary
They were entertaining. But what purpose did they serve? The only main thing they did was help Big Mama get Tod to Widow Tweed and yes, they also demonstated what Amos does to the animals. But were they really needed? Because their pursuit of the caterpillar didn't really figure into the story at all. Even a couple of read-alongs have not even mentioned them (they mentioned once in one of them but only that they were pursuing a caterpillar). Perhaps if they had come to Tod's rescue during the bear fight, that would have made them more necessary. On the other hand, it might've ruined an already greatly animated scene.
"HOPSCOTCH!"