Is this hard to start on my own? Do I need my CPA to do it?
No and no. Go here
to do it yourself.
How long does it take to get up and running?
I opened my first one about 5 years ago. Account opening was immediate, from what I remember, but nothing happens really until funds are deposited. Length of time depends on how you fund it (bank draft, check deposit, etc)
If I open it prior to April 15 does it count for tax year 2012?
I am fairly certain deposits must be made prior to 12/31 for the deposits to be claimed in that tax year.
Thinking of putting more in the youngest's and staggering down to the oldest. Is this a decent way of approaching this?
Actually, the oldest has the shortest time line so I would think to it would be more beneficial to do it in reverse from what you said. If the oldest does not exhaust the account balance, it can be used for the younger siblings. More Q & A here
Over all, La seems to have a done a good job with this and I have been very satisfied with it. I haven't had a child hit college yet so the jury is still somewhat out. Good luck.