I bet the ones from the mint are proof sets and the others are uncirculated. I used to buy rolls of 20 eagles for under 125 bucks, sold when silver went up. It's a cool thing to do for your child but you are not going to make money only loose it, I read that didn't matter so no big deal. 10 coin proof sets won't be as volatile.you can look at the link below to see what happens over the years with values. There are silver and gold bullion websites as well that sell direct. It's all good to buy if prices are historically low.
http://www.pcgs.com/prices/