Another thing I'm concerned about is the lack of resources in Orleans. Essentially, here's what I did when I tried it yesterday.
1. After getting the carts to Orleans, I advanced to the Castle Age.
2. I built an Archery Range, Siege Workshop, Castle, and Monastery within Orleans's Walls and positioned my army North of the cathedral.
3. Buy resources and create troops.
4. Research technology to improve troop effectiveness.
5. Have a regiment of 5 Knights, 5 Throwing Axemen, 1 Monk, and 1 Light Cavalry north of the cathedral.
6. Send all other troops to assault Southern Castle. Mangonels attack it, but get destroyed quickly because of arrows from the castle. Everybody else stands by to protect the Mangonels.