Sittler is a bargain basement #1 center, but you know that already. I didn't know anything about his defensive ability before this draft, but it seems like multiple old Maple Leaf fans have fond memories of it, which can only be a plus.
Sittler actually has better goal scoring numbers than playmaking numbers, so it's good you have an underrated playmaker on LW in Olmstead to help feed Geoffrion. This line is very well equipped to win physical battles with Olmstead there. Olmstead apparently also had something of a defensive game himself, though I wouldn't call him elite in that regards.
And of course, Geoffrion is an excellent triggerman (and very clutch too) who can take care of himself.
The first line by itself relies on a relatively weak #1 center to bring the play up the ice (neither Olmstead or Geoffrion was much of a puck carrier, from what I understand). Enter Larry Robinson - his excellent transition ability is definitely key to this 5 man unit.
Robinson is one of the most valuable defensemen in the draft at even strength - he's just so good in every way possible. Allan Stanley is a bit below average for a #2 in my opinion, but not bad by any means. His first pass and ability to put up points from the blueline will help. Robinson compensates greatly for Stanley's lack of footspeed.
Parent is obviously above average. I think it's unlikely that goaltending will lose you a series.