If it was me I would probably want something after the first tri. I don't think it's jinxing it I just think it depends on the people. If they are the types that will start spreading the news sooner than later then I say send them something sooner. But if they are more the type where they are going to keep the news to themselves until further along, then I would wait.
Or maybe send a card with a dinner gift card or something and then a baby related later?
I think sending a card and a small gift (basket of morning sickness friendly goodies?) is appropriate and sweet, but I agree that you should hold of on sending anything for the baby until she is further along.