I think the sleeves are going to be too long. And they have a decided tendency to stretch out even longer while wearing them. So after re-knitting the first sleeve last night to make it a bit longer, I will now be ripping out the cuffs plus an inch of actual sleeve in order to re-knit the cuffs at the original sleeve length. On the other hand, I think the armscye depth thing will be ok, so that's good.
I picked up some buttons on the way home from work that I think will work ok. I'm not 100% certain about them being exactly right, but I think they'll do for now. Sis is perfectly capable of replacing the buttons if she chooses to do so.
Overall, I think I'm pleased with the sweater design though I'm not terribly pleased with the hand of the fabric. It's a bit limp and stretchy for my tastes though I did meet the gauge that the pattern requested. If I make another one, I'll go down a needle size or two with this particular yarn (Cascade 220) to get a firmer hand. I'll give Sis an option to have a less stretchy sweater if she's not so keen on the hand of her birthday present too. (If I do re-knit, I'll carry the raglan increases down a bit further too so as to avoid the armpit tightness concern I had.)