How long could I keep egg nog?

Home made --- 1 week max. But then again, pop in some good rum, say to heck with calories and have a partee.

If you are using raw eggs, I wouldn't push your luck. Mayo with raw eggs shouldn't keep more than a week, at the most. Since eggnog has more eggs, I would say far less time. Once the eggnog comes to room temp the first time, you probably need to drink it or throw it away. I think it should be fine if you make it the day before a party (or maybe even 2 days), but get it in the fridge quickly and drink it all at once if you leave it sitting out at the party.
I think you will be fine making half a recipe ...just taste to adjust the seasoning because you might want slightly more bourbon or nutmeg.
Have a good party!