Best to avoid this place anytime July and August as is gets overpoplulated.  So much so that you can only book a 4 hr morning visit or afternoon visit.

We went in late September and it was great.  

The walk to the Grotto from the parking lot takes about 20 minutes.  The trails are groomed and easy to walk.  Although once you reach the Grotto, good footwear is required and you should be able to handle rough conditions.

The entire road surface is paved

This area is part of the Bruce Trail System