I suspect the bicycle show is an indoor event, at an arena or similar? If so, they will drive there in air conditioned car, and the event will be air conditioned as well, or at least cool because it is indoors. The only issue I see would be getting from parking to the event.
People do need to be sensible during a heat wave, and spend a minimum amount of time in the sun, or places where there is no breeze. Older people are more susceptible to heat stoke because our bodies do not regulate as well as when we were younger, nor does the body give the proper signals to the brain that it is overheating until too late.
We are in an area that most places do not have air conditioning, so air circulation, drawing drapes or lowering blinds, and opening doors or windows to create a cross-breeze are good ways to limit heat.