Welcome to UKCS.
If there isn’t a deluge of suggestions, use the site search here, tick for open all year (and anything else that’s important) and probably on-site bar or restaurant. Then check their websites or FB pages.
You might also want to check for towns having parties, that you can walk to from the site. I knew of at least two towns up here that have street parties or beach BBQs; they’re too far away for you, but there might be something similar in the NW.
Good luck.
Holgates have a number of caravan parks in the north west and they usually do family events for various annual occasions. For example, we were at Bay View last weekend and they had a bonfire, fireworks and BBQ for bonfire night and children’s activities such as a pumpkin hunt, halloween fancy dress completion and seasonal crafts during the day. I am sure they will have new year stuff going on. Bay View is their quieter site but if you want somewhere with a pool etc, look at their Silverdale site.
Amazing family weekend with old steam engines, classic car displays, market stalls, and full catering and bar. And camping on site - Save £25 by booking in advance.