I'm having a hard time trying to figure out the timing of visiting these sites. I originally wanted to get to SF first to avoid the crowds but being that PG opens at 8 am I opted to purchase tickets for that. I would love to enjoy SF without the crowds but I'm guessing that won't happen since I doubt I'll be able to get to SF by the 9 am opening time. Hospital has a one hour 10:30 am guided tour which would work well after PG. What time should I book for SF? Or am I better off doing SF first thing the following morning?
You don't need a guided tour at Sant Pau. Take your time and enjoy it. It's about a 15 minute stroll from SF along Av. de Gaudi, past lots of tempting restaurants. I haven't been to PG so I have no sense of how long a visit would be or how long it would take to get to either of the other sights.
Over the years I've been to Park Guell maybe 3 or 4 times, and I think I prefer it later in the afternoon.
Start your day at Sagrada Familia, then stroll up Avinguda Gaudi to the Hospital Sant Pau site. On the way, check out possibilities for lunch later on. Bus #92 will take you from nearby Carrer Sant Antoni Maria Claret to Park Guell.
https://www.tmb.cat/en/barcelona-transport/map/bus