OS X :: Setting Up Users For First Time?

I am setting up a new iMac for my parents and since I'm a noob to macs myself (had one for only a few months now) I was wondering what's the best way to set up user accounts. I need to create two accounts so ma/pa can log in and access their own settings, look and feel etc. They are moving from windows XP where they had their own user profiles (dad would leave his desktop littered with icons while mom kept hers nice and clean) so I need to keep two profiles otherwise this would confuse them. I guess my most important questions are:

1. Should I create a separate admin account first when setting up the iMac then create the addition two accounts, or just create two with one of them being an admin. I intend to put something like LogMeIn on there so I can remote in to do any maintenance for them, install apps etc.

2. Dad uses AOL mail and Mom uses Yahoo. I would like to setup Mail so that they can access their emails without using the web mail apps. Question: When the mail accounts are setup are they only seen when logged in under each user profile? In other words, will Dad only see his email in Mail then when Mom logs in she'll see her email etc. or will they both see each other's mail?