I would definitely have them work on basic forward, backward, lateral stepping before moving them on to movements that requires them to cross their feet over, turn, or zig-zag. Of course, have them move at a pace they are comfortable with before increasing speed.
Natalie, if tripping is a concern, then draw the ladder on the floor or use coloured tape on the floor to create the ladder. You don’t need a physical agility ladder to do any speed-agility-quickness drills. Even sedentary people can benefit from such drills. They likely need it more than the elite athletes who regularly trains on a daily basis.