Well everyone suggests something else but I never had any bother with Powerpoint, each time I've forgotten how to use but soon got away with it. Not putting down all the other suggestions but Ppt is on the machine itself so doesn't need any internet or support. The finished file can be put on a usb stick but of course the computer at the show venue must have the Ppt programme, or take your own laptop.
Makers of things to sell are forever producing new versions when the original had more than enough features for most of us.
But you've probably done the show by now.