Gas Generator how many watts!!!

Looks like 800 watts plus the lights. 1000 watts would be minimum. I would go with a Honda. It is probably a lot cleaner power compared to the cheap models from Harbor Freight. There's a reason why they are cheap.
That's not much headroom. Which is why I suggested 2KW. I would go at least 1500min. Anything on the order of PA/ music is not a stable load, like lights or similar. Sound system loads are all over the place, with very high peaks. More like motor starting loads I would give that a fair amount of headroom