Can anyone give me a recommendation to a laptop that would run this well without generating a ton of heat. Would a dual-core laptop help?

yeah a dual core would work, plus get at least 2 gigs of ram if it is running vista, and a graphics card of at least 128 memory.

The most important thing for gaming on a laptop is getting one with a discrete graphics card. Many laptops use integrated graphics to save on battery power and price, but you really need a discrete card that has a pixel shader and vertex shader capability.

To be honest with you, my best experience on Civ IV on a laptop is my wife's MacBook Pro (the Pro, not the regular one). I have Windows XP installed on it in bootcamp, and Civ IV, BTS runs great on it. Expensive though - (~$2000), we didn't buy it for Civ obviously. It is her computer for work.