Welcome to planDisney, Brenda. I'm so happy you brought your question to us, as hailing from the UK, the concept and theming of
Sci-Fi Dine-In Theater Restaurant makes all my Americana dreams come true! It's also the perfect break from the Florida sunshine as it's themed at night with sky full of twinkling stars.
Advanced dining reservations open up 60 days before your arrival date, and, as you have already encountered, popular spots book up quickly. The seating arrangements in Sci-Fi Dine-In Theater Restaurant in
Disney's Hollywood Studios are unique, with drive-in style tables for two, which may be why you can see availability, but not for four people as they are unlikely to be seated together. Perhaps booking two separate bookings, close together in time, is an option. You could speak with the ever-friendly cast members at check-in and see if there is any space to seat the two parties together, subject to availability.
People's plans change frequently at Walt Disney World, so my other suggestion is to keep checking availability as the exact booking you want may become free. Please know that you may modify or
cancel any existing booking up to 2 hours ahead of the reservation time (within 2 hours, there is a $10 per-person fee).
Brenda, I hope this helps. I'm sending all my pixie-dusted Disney wishes that you secure the dining reservation you want. Please reach out with any other questions ahead of your adventure, Louise.