First time cruiser - dining time question

I'm looking to book a cruise on short notice, and it'll be my first one. I noticed it's asking you to pick a dinner time, and for this particular cruise, only the 8:30 time slot is available. That seems quite late to eat dinner every night, especially after a long day. Are there any other dining options, or how does this work? Also, won't you be missing the nightly entertainment if dining at 8:30 every night?