Thanks for the link @asleepattheshop , I think planning what to say is a good idea, not just so you can resist peer pressure, but because you are also priming yourself to keep it moderate.
Depending on the nature of the friendships, you could possibly make a joke about it... something like "Are you saying I'm rubbish company when I'm sober?!", said with a laugh and a wink, might be preferable to just repeatedly saying no. You could also explain that your tolerance will be lower than usual due to taking a month off drinking, which is of course true. I bet there will be a fair few people with giant hangovers on 2nd Feb, because of this.
Good luck tomorrow and enjoy your evening 🙂