Stay tuned on converter information. I'm exploring options that might work with just cables that might be less expensive. Otherwise, see below.
Reflection App for PC or Mac - No Apple TV Required - $8 - $14.99
AirServer App - No Apple TV Required - $14.99
Pricing and Ordering Information
Direct from Apple using a School PO
Apple TV - MD199LL/A - $99
The following items were from Amazon.com
HDMI to VGA Converter or This Link
Some may need this video splitter (Some may already have this in place)
Video Splitter (Switch from Apple TV/Ipad Display to Computer Display
I found these locations to purchase - here and here - There are many more.
This is not an endorsement of any vendor, but who you might order from and things that you 'might' need.
Shared Google Doc Link to Presentation