Demonstrational smelting iron
The biggest problem you will have is getting a high enough temperature, not the oxidation of the iron.

Putting the crucible in a charcoal furnace won't produce a high enough temperature to cause the reaction or the liquefy the iron: you need to have a crucible that can be driven to a much higher temperature. Normally this is done by blowing air (or, if you have it, oxygen) into the furnace. In practice what is often done is to mix the iron oxide and an excess of carbon in a single vessel: the carbon burns to create the temperature and also acts as the reducing agent to create the iron. This still requires a source to force air into the mixture. This appears to be how ancient craftsmen did the reaction, kicking off the iron age. 

For an account of how to do this see this blog describing a modern recreation of some of those ancient techniques.