I'm not a concrete expert. But can offer you this advice.
1) This is not a buy bags and mix it yourself project.
2) Your delivery company can advise you as to the quantity needed. My guess is 3", maybe 4", probably not 2"
3) there is fiber reinforced ready mixes that may be ideal for your situation and not require a mesh. Ask your supplier.
4) Finishing a large area properly is an art. Consider hiring it out.
Also - make sure any water issues are dealt with now. You dont want to have to bust up the concrete after the slab is poured to add french drains or a sump pump.
The Handyguys Podcast [url]http://www.handyguyspodcast.com[/url]