Knitting project

So I'm making a pair of horizonally ribbed arm warmers from my own non-existent pattern. For the most part it's been fantastically easy. Basically I've done a ribbed pattern along the lines of a scarf. The plan is to add buttons to it to close it off and make it adjustable since I'm also planning to make it relatively long -- from knuckles to elbow, hopefully.

Here's my problem, the last time I tried to make it, it was strictly an arm warmer so my mini-scarf pattern totally worked. (Tried b/c I had to toss out my project due to a bit of a house disaster.) Now that I'm making it so long, and b/c my arms get kinda fat, I'm thinking that I have to accomodate both the width of my hand and the the width of the upper part of my arm.

Anyone have any ideas? Should I increase for the area around my wrist, and then increase again near my upper arm? Make the whole thing big and just futz around with the placement of the buttons? If it helps, I'm doing this on straight needles, about 91 (or maybe 93) stitches cast on. There's a couple of pictures below the cut of what it looks like now, and what it should look like when I'm done.

( Pictures here )

crossposted to novice_knitters