YANBU
My Ds1 wants a DS, he is coming up for 5 and has intermittently asked for one, whenever he has been in the company of other (slightly older) children who have them.
I personally think they are a bit anti-social (based on experience of cousins of 7, and 11 excluding my ds when we were all visiting. The visit was meant to be a joining the family together again visit after a fall-out of 7 yrs or so, but was nothing to do with me. I realise that this obviously makes me biased, and you could say my ds was a bit young for these cousins, but he is very clever and articulate and can certainly hold his own. The cousins still play with toys that my DS won't touch, as they are for babies!! ) and I also don't like the lack of activity they encourage.
Having said that, he only really wants one when he sees other children with them. For Christmas, he got a Vtech Storio, which he loves and is very educational. He will be starting school in August and I wanted him to start using technology. I am aware that he is inactive when he's playing with it, but the weather has been so bad that we've hardly been ou, and he likes to play it in bed at night.
I know children of 7 who got those Tablet thingies for Christmas, as well as other hi-tech items.
I will get him a DS when he is older, but will be avoiding it as long as possible.
I'm not judging anyone who has these things for their DC at a young age, each to their own! But OP, I don't think YABU at all!