Venice Tourist Card. (Venezia Unica)

I am a little late to get going on this as I fly out Friday at noon so would really appreciate the wisdom and advice from you who have done it before.

After hours of researching and a computer meltdown in the middle of it all I finally figured out how to load and pay for the things I wanted on the card.

In the Museum package it includes among other things, entry to the Doges Palace. So I have a voucher showing I have paid but I would think that one would also have to book a date and time for admittance but cannot see how to do it anywhere on the Venezia Unica site.

Also same for the Venice Opera Theater tour.

Or is it possible that I will easily get in without prereserving a date/time if I just show up with my prepaid vouchers?

Also have paid for vouchers for museums at Murano and Burano, but assume they would be a little less busy so would not require prereserving time/date?

I have had such wonderful guidance from so many of you before so I hope you can come to my rescue again.