This was a very endearing first chapter! The Bentley's—especially the children—are a rather raucous bunch! I think you handled the dialogue among the children incredibly well; they're ill-mannered and bratty and fight among one another in a manner that's both logical and consistent with sibling behavior. And this mouse family is certainly well-to-do! Their manor has 15 bathrooms! I'm not even sure I've ever seen a mouse use the bathroom and I can assure you I am not looking it up either

The line the Bentley children were completely blind to it immediately brought me back to my childhood. I know there are four Bentley children, but it made me instantly think of the Three Blind Mice. Blind leading the Blind. Nice touch!

I also enjoyed the stuttering cadence in which Mr. Duffle speaks. Parts of words are repeated in just the right amount of "flavor" so as to show Mr. Duffle's speech impediment without it being distracting or annoying to read.

I would suggest breaking up the big block of expository prose you have at the beginning of the piece. It's a big info dump. Sure, it sets the scene, but it'd be more entertaining to read this information interspersed with the actual action of the scene. I'd suggest starting your scene with the action (Mr. Duffle's knock on the door) and work the beginning of your story and the exposition around the arguing of who's going to answer the door. I think it'd make for a better reading experience.

You also touched lightly on the fact that Mr. Bentley is a lawyer and allude that mice do in fact need lawyers but never give any reasons. I like the tongue-in-cheek humor of this but think it might be more effective if you carry the bit on a little longer and include some funny things mice may need a lawyer for: property disputes with other animals trying to take or run them out of their dwelling, accident/insurance claims and orders of protection stemming from cats, class action lawsuits against mouse trap manufacturers, and family court over the paternity of mouse pups since mice tend to breed quite a bit.

The last area I'd like to mention for improvement is the ending. I think it's great that you leave it on a cliffhanger! But I think it can be more effective if there was more of a buildup rather than just plopped on to the reader. Mr. and Mrs. Bentley walk into a room and start arguing. The reason for the fight can intrigue the reader but there has to be the setup for it first. Right now, the action doesn't seem to leave the reader really hanging on to the edge of their seats. I'd suggest reworking the ending. Maybe one of the children overhears a line or two of their parents' dialogue that sets the stage for a mystery. You've already got the father's red eyes and what that entails. Stay in the mystery realm and leave the readers guessing what's really going on.