ladybrewer - glad to see you're trying to concoct some butterbeer! I've also cooked up a recipe recently posted a few days ago in this thread. If it helps, I'll provide some of the though process that I used in making my recipe:
First, I wanted something that would be an opaue tan/orange color. That's why I went with pale 2-row, wheat, and caramel 40L for the malts. I actually just watched the Half Blood Prince last night and saw this scene in the Three Broomsticks after Hermoine orders "three butterbeers":
I was really happy because the color seemed pretty close!
As far as taste -- I heard that the "butterbeer" they're serving up at the new Harry Potter theme park is like a very nice cream soda. That seemed about right, so I thought vanilla should be a primary flavor (vanilla beans in secondary). Furthermore, I thought a sweet, caramely, butterscotchy taste would be pair nicely with the vanilla. Also, I wanted it to be somewhat low alcohol, perhaps 5% or less (after all...these are kids that are drinking this stuff in the books).
From the recipe you've drafted up, it seems like you'll have a toasty, malty, spicy brew. I would guess you'd come out at a brown color with the grain bill you've proposed. I would question the necessity of the munich, aromatic malt, special roast, and vienna. Mostly because I think these would darken the beer beyond the color you see in the picture above. Also, some of those malts would add (perhaps unnecessary) roasty/toasty flavors. Honey malt could be good -- I thought about adding it myself. Why not also add a little wheat to give it that opaque appearance?
The other additions look pretty good. I decided to stick to butterscotch Schnapps for bottling instead of the extract. Previous posts indicated that the extract is just far too powerful. Also, you could add the lactose during boiling or bottling -- doesn't really matter.
I just racked mine to secondary last weekend. I'll repost upon bottling in a couple weeks. Hope all this rambling was useful...