Use this app:
EV Trip Planner
Plug in the round trip, car type (use 60 as there is no 70 option), conditions (temperature) and you will see that you do need to charge either on way there/back/both.
I helpfully plugged in this for the total journey (Markham -> Collingwood -> Barrie) using a Model S 60 to check your scenario:
Speed Multiplier 1.2 (presumes you will be driving at speed of traffic on 400, namely, 115 km/h or more)
Cabin Temp (°C) 22.2
Ext Temp (°C) 2
Distance 199.9 km
Driving Time 2:06
Total Energy Used 48.6 kWh 261 RKM
Average Efficiency 243 Wh/km
Looks like you will need to charge only on the return leg. 70D should have more than enough RKM (rated km) if you range charge to 100% at home before you start. You only need 261 RKM to get back to the supercharger on your return leg, probably will have 100 RKM remaining when you plug in.
Story:
We went to Gravenhurst (much further than Collingwood) from north Toronto last month and charged for 20 minutes on the way there (and grabbed a quick snack at McD's) and one hour on way home (to eat dinner).
We actually charged briefly on the way there because I forgot to range charge and we left home with only 80% battery, and wanted to make sure our day trips in Gravenhurst were not going to be a problem. If we had ranged charged to 100% our S85 like we normally do for long trips, we'd have only needed to use supercharger on the return trip leg.
Addendum:
Do NOT forget to range charge. My wife was not impressed with me on this mistake. She plugs her Tesla in at all times when it's in the garage, and expects it to charge to 90% every night, on the off chance we need to be able to drive anywhere in North America the next morning (I'm only half joking), so we always leave the charging to 90% (the default), and only change to 100% for big trips like this. I simply forgot to set the limit to 100% the night before. ARGGG!!! Oh well, I happen to like McD's fries once in a (long) while...