I would usually just add Flowerfest as a holiday in spring, with the Flowerbunny and egg search. A couple of times I've also added a holiday in summer, with BBQ and water fun. I've also added costumes and trick&treat in a couple saves. Not really deleted any holidays, but I have mods to remove most of the random days, like Neighbourhood brawl and Rebate day. With only 7 days in a season, I don't want too many holidays. I usually forget to do the same changes in every save.
I've not created many clubs. I have a couple for some saves for my vampire friends to meet up and party/hang out/work on skills. There are only 3-4 existing clubs that are not useless, so my sims don't join clubs much.
