Tom, you should be fine. The system is relayed with a 15 amp relay already. Just wire them in. I wired 50 watt H3 foglights to my existing system and no difficulties.
One warning. If you use the small H3 type lamps in your foglights, they need to dissapate heat and they are generally mounted to a metal frame/reflector in the light, even if the housing is plastic.
Often, that frame then grounds to the body through the mounting brackets.
So, observe polarity! The wires from the foglamp may not be interchangeable so connect black to black when you wire them in or you may blow a fuse. This esteemed, allegedly educated engineer did just that (wired them wrong) and popped the fuse the first time I tried them -- and a couple of times after until I figured out I'd reversed it on one light! DOH!!!!