warning light on 2000 Cadillac DeVille

my husband used our family vechile to take 4 golf buddies and 4 golf bags to a golf outing. when he returned the check engine light was on. could this be due to hauling a heavy load?

Asked by for the 2000 Cadillac DeVille
Was the engine Ping-ing? ok, dumb golf joke.
The check engine light will come on when a fault is detected in the emissions system. It's possible that there has been a problem for awhile, but the problem was not quite bad enough to set the light, but the extra load pushed it past it's threshold. My main point here is that the problem was there already, and it was not likely caused by the 4 golfers.
You'll need to get the diagnostic codes read out to determine what to do next. If you get the codes and post them here, we can further direct you as to what to do. Some auto parts stores will do this for free, or you can buy an inexpensive scan tool. Or, if you have a repair shop that you take your car to, take it in and have them check it out.