I once won a pie contest with a chocolate cream pie. It’s decadent, delicious, and you cover it with whipped cream, so you don’t need to spend a long time decorating.
I don’t have the recipe I used on hand, but this one looks similar:
https://cooking.nytimes.com/recipes/1019473-chocolate-cream-pie-with-oreo-crust
Use the best chocolate you can get. Make the crust yourself- it will be better than the premade Oreo crust and it’s not time consuming. Add the whipped cream at the last minute. If you need to whip it in advance, bring a whisk and whisk it for a few seconds to refresh it before adding.
Good luck!