When asking for cash or gift cards, I think it's nice to focus on the ITEM that you want to get. (like a bridal couple saying on their registry: "we need to buy a washer & dryer for our new home, so any monetary gifts will be earmarked for that"--it means I can think about the *thing* when I'm writing my check. And it implies that you'd get it anyway, and that non-monetary gifts wouldn't be UNwelcome--it's just that if you decided to give us money, that's what we'd use it for)
I don't think you need to get into much detail. Hey, you want it. That's all they care about, really, right?
I think it might be good to offer some smaller, more tangible things in case they really want those sorts of ideas. But make them the SECOND thought.
Perhaps say, "The one thing I really want is a tablet computer. So a contribution to that would be great. Or if you'd rather, I need new turtlenecks in pretty colors for work. And Netflix membership would be great, because I could send the DVDs back, and I wouldn't have to find somewhere to keep them."
(but then, I'm a fan of gift lists that go all over the place and have small and big stuff on it. I once put waxed paper on mine, bcs I couldn't find it at my grocery stores at the time. At all. But I was disappointed bcs nobody ever got it for me--not even the young nephew, who I was hoping would decide it was within his budget and he knew what it was.)