really depends on preference. I have a 12x12 dining room currently and in my "new" house have taken down the wall between the kitchen and dining room to make an informal dining room, this will be about 13x12.

11x12 is still a dining room, it isn't all that large, but I don't know if that is a problem in your house, only people who have seen the floorplan could really tell. you're not going to be having large dinners in a room that size unless its open to more space.

Replies to this will likely be in the form of opinions, so here's mine. I am going to assume you are in the US. I believe US society is drifting away from traditions like formal living rooms and dining rooms toward functional spaces, which is what you're doing. We did the same thing with our formal LR and instead call it the Study, and it holds our computer equipment and other such office stuff.

A larger kitchen will make you happier and increase the value of the house or at least make it a tie-breaker in a buyer's market.

In terms of resale, a spacious kitchen plus small dining room is preferable to a spacious dining room but a small kitchen. Kitchens are just a much higher priority for most people.

Thanks for your input. I think I am going for it! A bigger kitchen will make me happy- and I'm sure guests will enjoy it too!