Looks great! Since you've done a tank top, I'm assuming you know how to check your tension before beginning by knitting up a swatch? Just making sure, because even if your tension is off by 1/2 stitch, the cover will come out way too big or small!
Also-- if you've never done short rows before-- this pattern has them. They are very easy; what you're doing is just before you get to the very end of the row (by whatever they tell you-- I think the first time it's 3 sts), you turn AS IF YOU HAD FINISHED THE ROW and start the next row.
I'm sure he'll love it!