Yes, there are drawbacks (especially the taxes ones) but I think the wave of citizenship renunciations going on are a sign that the strange treatment of non-residents will change in the next couple of years. FATCA is the best thing to happen to US taxpayers abroad in a long time.
I think the benefits outweigh the costs. If they don't get it before their 18th birthday, it will be much harder. They can always renounce it later, though.
Having traveled a lot, having a US passport is very beneficial for ease of passage across borders and protection when abroad. EU passports are almost at the same level though.
Take a look at this article: http://www.economist.com/node/... It has some good information about it.