Bears and Deacs
Bourbon Drinker
Evan Williams bottled in bond (white label) which has enough proof to hold up when adding all that ice.
Edit: I see now that it is for 150-200 people, most of whom probably won’t care about the bourbon flavor. So in that case I’d get cheap handles of bourbon that actually state “straight bourbon whiskey” on them.
This is what I would go with as well (and what I use every year). It’s $25ish a handle where I am so not too bad. It could be diluted by adding 200ml of water per handle to drop the proof to about 90. That would help stretch it a bit.