I'm under the impression their the same thing... You can get a Large Can of Brine Shrimp eggs for a Much lower price then a Sea Monkey kit online. With tons of DIY info on making a hatching system...
They sell brine shrimp hatcheries and eggs online and in aquaria catalogs so they should be fine as a food source, depending on what type of fry you want to feed them to
Yes, your Fry would go after them depending on what your Fry are... Just remember it's much cheaper to get Brine Shrimp and a Hatchery then it is to buy Sea Monkeys... Sea Monkeys are targeted at a childrens' market and are WAY Over Priced.