Most LED lights use a driver the provides the proper voltage for the LEDs regardless of input voltage. Many will operate just fine anywhere from 10 up to 30+ volts.
The biggest thing to worry about on a golf cart is the current draw coming from only two batteries. It will eventually make those two out of balance with the rest of the pack and can damage them due to undercharging, and cause damage to the other batteries by causing them to overcharge. Batteries are alot more expensive than a reducer.
The reducers sold by ScottyB at Cartsunlimited are easy to install and work with the key switch so they don't draw power when the cart is not in use. He also provides clear wire diagrams for installation.
http://www.cartsunlimited.net/12v-reducers.html