Cutting the guest list

Love your date! It's my birthday lol. As far as having to cut down your list, I think it would be proper etiquette and just a simple courtesy to let those you are having to cut know that you can no longer accommodate them. You can obviously just use it as a template or keep it how it is but maybe you can say something like:

"Due to the newly placed Covid-19 restrictions at our venue, we are forced to downsize. It is with a heavy heart that we can no longer accommodate your attendance. We hope you understand and you will be missed. Thank you."

I would definitely tell them because receiving a save the date, people can still look forward to it and plan for it.

if you are able to, can you livestream so those who cannot attend can see?

you can say something like "unfortunately due to venue limitations and safety concerns as a result of covid-19, we are required to reconfigure our guest list."

Agree that you absolutely need to reach out to these people and explain the situation. Whenever I receive a save the date, I do exactly that--save the date. I'm sure they will be very understanding given the situation, but they need to be informed

You should definitely say something, but I think people will be understanding. The point of the STD is to get them to hold off all other plans on that date, so if they can change their plans that day, they need to know.

Before you send out anything, go through your list. Those that don't make the cut, call them directly and let them know. You can say something like:

Hey, (insert name) This is Melanie. I'm calling about a change to our guest list due to the restrictions COVID-19 has mandated on our venue. We sent you a Save the Date back in (insert month) and regret that due to the social distancing restrictions, we had to make dramatic cuts to our guest list and are limiting guests to family. Please accept my apologies as I sincerely regret having to make this call and hope you will understand.