I literally have an entire spare bedroom FULL of gear. DH is obsessed.
IMO the best of the dry snorkels are -
XsScuba Dry Goby Snorkel for kids -
www.cheapscubagear.com/3949-XS-Scuba-Goby-Dry-Snorkel.html
It's totally dry and has a smaller bite piece that most kids can use, even with some missing teeth.
Ocean Master Dry Snorkel (for the big kids)
www.cheapscubagear.com/3428-Ocean-Master-Dry-Snorkels-FLEX.html
This is the top of line the dry model. All of the Ocean Master Dry Snorkels are good, but this one is really comfortable.
Masks really depend on your face shape. You need to try it on. For kids, we really like the Deep See masks. They are durable, fit all the kids (from a 4 year old up to even me) and we haven't had any leaks.
www.snorkelcity.com/deepseeminki.html
I recommend getting a neoprene mask strap cover, really makes it easier to get on and off. They cost $5 to $7.
Unless your kids are coordinated swimmers or they can practice in a pool, skip the fins or get the short swimming ones. This is a skill that usually needs some practice and kids tend to wear themselves out trying to master it and concentrate on the snorkel too.
And, once again, the mighty Volcano God (hahoo wahee, hahoo wahee) is right. Dry snorkels are way too bulky for scuba and rash guards or lycra skins offer great protection. I never snorkel without at least a rash guard top on. Cuts way down on the sunscreen needs.
Happy snorkeling!
Noel
edited to add -
If you are going to practice in a pool, MAKE SURE YOU RINSE YOUR GEAR. We wash our stuff in a bath of water & Simple Green after every use, whether it's the pool or ocean. Chlorine will destroy it quick though.