If you're writing children's fiction a good move is to join SCBWI. They run lots of events where you can meet editors and agents. Their weekend retreat is very popular and worth going to, but book early.
Another way to get names is to a) get the generic email address of the publisher then b) search blogs, etc, to find editors' names (this can be useful in that you can refer to their blog/talk, etc, in your cover letter). You could also join Publishers' Marketplace ($20 per month) which has loads of US and a fair few UK editors' addresses (no reason you can't submit to US publishers anyway). You could also try:
http://everyonewhosanyone.com/index.html where there are lots of editors' email addresses - but I'd double-check them first since this isn't a totally reliable source.
Cover letter/synopsis/three chapters is the traditional submission package, e.g. what publishers used to ask for and what many agents now ask for. A query is shorter: as said, it's more of a selling document. If the publisher is interested, they'll probably then ask for the first 3 chapters or the whole ms. The good thing about a query is it gives you the chance to show you can be professional. Which is the key to all this, i.e. publishers are professionals, therefore any approach you make should also be professional and display you have an understanding of how the industry works (regardless of how artistically brilliant your book might be!).