Both the traditional collar and snap collar are appropriate. The snap collar may be more fashionable in certain areas, but both are totally acceptable. You really can't tell the difference from a distance. For good deals, check out the Essex Outlet. Smartpak also has some nice shirts, both snap collar and traditional collar, in the sale section right now. Smartpak offers a great return policy if the size doesn't work out.
No pin. Some may still monogram, but it's done less and less. If it isn't monogrammed already, I wouldn't waste the time/money to get it done. Just my personal opinion.
If you're looking for kids shirts, I'd check a consignment store or ebay. Sometimes you can find the really nice ones for nothing (says the person who has a closet full of Essex and Van Teal shirts purchased for around $10 each).