While DIY can be fun, I prefer to buy a finished product when there's a solution readily available... Especially when dealing with home wiring.
When faced with a similar problem (big room, wanted to control multiple lights without pulling wires), I used an Insteon battery operated remote switch:
One advantage of the off the shelf products is that they are all UL approved for the use, so if it catches fire and burns my house down, I don't have to prove that it wasn't my fault.