St. Catharines is a comfortable base for the Niagara region rather than a checklist of city attractions in its own right. The Welland Canal, the Henley Regatta course, the wineries strung along the Bench, and the short drive to Niagara-on-the-Lake or the Falls give a week's worth of things to do without ever having to stay in a Falls hotel.
Within the city itself, head to Lock 3 to watch lake freighters transit the canal, take a stroll through Port Dalhousie, and time a visit around a Niagara IceDogs game at the Meridian Centre if you can.