I have heard it is a very hard to get reservation.
If I am logged in and ready to go right at 7am exactly 60 days out from our vacation dates, am I likely to be able to reserve this for the 4 of us? Or is it just luck bc so many are also trying to do the same thing I am?
It is an “enchanting extra” and those offerings open early. I booked my dessert party at 4:40am but I have read many reports that enchanting extras often open up after midnight on day 60 (so by 1am). All booking open by 6am, online.
Oh thank you! I have never booked an EE. I will be super excited if I can get SS. 
For onsite guests, ADRs dont start until 6 am then on day 60?
Yes. Remember you can do 60 days plus length of stay (up to 10).
SS typically sells out 66-68 days ahead, partly because the capacity is only 12 people for each tour. The first tour of the night sells out first.
I experienced varied booking times. Some days were midnight, other days opened at 4am. Booking from the app seemed to be faster/earlier.
I have one night at ASS and 8 nights at AKL. The first night does not unlock the rest of my stay. So I have to try again tomorrow.
You can have Mouse Dining look for a reservation for Starlight Safari. I was able to get one in a couple weeks the other day using it.
I successfully booked our 4 slots for the Starlight Safari!
Things I learned:
A split stay doesn’t unlock your second resort reservation’s dates on the calendar - you only get access based on the first one.
Reservations didn’t open right at midnight, they started at 12:04 AM. 
I was refreshing since midnight and nearly gave up when… boom! It finally opened.
I initially booked 60+6, but then I had time to go back and switch it to the 60+4 I actually wanted.
The 8:30 pm slot sold out super fast within a minute I think! The 10 pm slot was gone in about 4 minutes.
I was just able to get a reservation for 2 for May 2 using the free version of Mouse Dining! I originally had tried at 60 days but didn’t try until late morning and there was only 1 spot available, and that one spot was gone by the end of the day. I have been stalking and checking since then, but tonight I got a notification from Mouse Dining and was able to snag it!