The T3 sensor is more than 3x larger than the SX50 sensor. You don't need zoom range, you need the best image quality. For the 24-100mm range, it's no contest, the T3 + 24-105mm f/4L combination is better.

The one thing to be careful about: when using flash mounted on the camera, vertical shots can produce odd shadows to the side of the subject. Consider getting a Lite Genius Lite-Scoop II Flash Modifier. For candid shots, it can help soften shadows nicely.

Here is some advice for no matter what you use. I can always tell the newbies from the experienced event photographers by just looking at a couple of photos. Actually most kids these days come by this naturally, because of the "selfies" craze.

When taking photos of people, actually get their attention and ask them to turn around and look at the camera. Timid newbies take a lot of photos that show the backs of people's heads. You really won't get good images by trying to be a "fly on the wall." 99% of the people will move closer and smile just naturally, you don't have to pose them. The other 1% are probably wanted by the law and will be difficult no matter what you try, so ....their loss. Anyway, think of the group selfies that kids take everywhere, and try to get that close, happy look in your event photos. I try to get everyone at each table in at east 2 photos with different people from that table, or at some time in the event. With only 150 people, it won't be that hard.

Are you charging? If so, think about getting insurance. Even if your job just pays for the insurance, it is worth it for future shoots. There is a lot more to shooting for money than people realize. Insurance, taxes, sales tax, business licenses, etc. Often at the beginning, it is better to just ask them to give you a gift card, or some other gift in kind, so you don't have to get too much into the business side until you decide to really start doing it.