https://stlmardigras.org/
Most of the bars in Soulard and on Laclede's Landing should be busy with events. Be sure to lock up your car or take an Uber/Lyft if you plan on drinking.
I have heard that NOLA Mardi Gras is a little more wild but here they do warn any flashing of body parts for beads (I know, no fun right?) and things like public urination will end up with you taking a short staycation in our fine jail facilities.
Be safe and have fun