Suggestions for three-night/four day drive to St. Pete's, accomodations en

I can give you routes, but not cat friendly acccommodations or local restaurants.  It is best to figure out the local restaurants when you get to a place as the restaurant business is hard and even the good ones go out of business periodically.  And you can do a search in each location for pet friendly hotels.  Be advised that most of pet friendly accommodations mean that they allow dogs and not cats.
The distance from Toronto to Seminole Park is around 2200 miles and will take about 21 hours to drive.  For four days driving, this works out to about 5.5 hours of driving a day.  There are two basic routes - one goes through Detroit and down the middle of the US through Atlanta.  The other ones goes through Buffalo and to Savannah - there is one branch that goes through DC and the other one goes through Pittsburgh.  
I would avoid both Atlanta and D.C.  So I will suggest stops on the middle route going through Buffalo First stop a little south of Pittsburgh in Washington (Pennsylvania) (5.5 hours).  There are 8 pet friendly hotels there.  Next stop Fort Chiswell (5.5 hours),  Savannah  (5.5 hours) and then to St Petersburg (5.5 hours)

Hi Judy,
That's a doable itinerary - 3 nights and four days from Torontoto Downtown St Petersburg , FL. These are suggested stopping points with pet-friendly hotels:
Drive about 6 hours to Pittsburgh, about 320 miles (510 km) from Toronto. Stay at Hampton Inn Pittsburgh/Greentree. There's a $25 fee for a cat.
The next day, drive another 5.5 hours (310 miles) to Jonesville, VA. Stay at Best Western Plus Yadkin Valley Inn & Suites which is located less than 2 minutes' drive from the highway. There's a $20 fee for a cat.
I suggest stopping at Residence Inn by Marriott Savannah Airport before arriving at your final destination in St. Petersburg. This hotel charges a $100 fee for your cat. The drive from Jonesville to Pooler (a town about 13 miles from Savannah) is around 6.5 hours. Pooler is about a 6-hour drive to St. Petersburg.
Hope this info helps.