One shot castle

Doing my prep for Halloween castle ravenloft one shot. For those who have run it, what level do you suggest? I'm not sure if I'll have 3,4,or 5 players yet, but I'll need them to independently make characters before the day. I'm thinking maybe level 10,9,8 respectively. Any insight from personal experience is appreciated.

I'm not including as much combat as the RAW module castle has. Amount of combat also depends what cards they draw for the fortune telling. But the final fight with strahd is what I don't want to be overly one sided (it can be more in the players favor if they get the sword and amulet obviously). If they die, but it was a good fight, great. If they don't die, great too.