Hi paromo;
Barrie is approx. 58 miles / 94 km north of Toronto. From Toronto Pearson Int’l Airport;
• Highway (Hwy) 401 east to Hwy 400 north
• Hwy 400 north to Barrie
I’m sorry, but I am not familiar with the location of the resort, so I won’t comment on how to get there from Barrie.
Driving or using public transit will take a considerable amount of time out of your day when visiting Toronto.
For Niagara Falls & the 1000 Islands you will need to drive south into the Greater Toronto Area, (GTA) which is renowned for it’s traffic congestion, before turning southwest towards Niagara Falls (80 miles / 130 km from Toronto) or turning east towards the 1000 Islands (180 miles / 290 km from Toronto)
Respectfully, basing yourself in the Barrie area will be quite an inconvenience to visit Toronto, Niagara Falls and the 1000 Islands.
You should seriously consider MattInTO’s suggestion of breaking up your stay and spend some time in Toronto & the 1000 Island making Niagara Falls a day trip from Toronto.
Best Regards