BlackGarden, & SteveB from The Sims Resource have tons of information and screens from the Generations event.

Young Adults and Adults

One of the major new features for adults and young adults is of course the new bachelor and bachelorette parties. Once your Sim is engaged, they can now choose this party type, and they are just about as true to life as the developers could get away with, while keeping the game’s ‘T’ rating. Of course, your Sim might want to ask their best friend to make a toast to kick off the festivities, then the party can continue with plenty of nectar and dancing

Graham informed us that Sims will often strip off at bachelor parties, so at the end of the night you end up with a bunch of men passed out on the floor in their underwear. Maybe those Sims will remember the dancers. There seems to be a variety of different outfits that the dancers at bachelor and bachelorette parties will arrive in. These include firefighters, soldiers, and police officers. There is also a new interaction which will allow you to spray other Sims with fizzy nectar. How they react depends on the Sim, of course.

For the actual wedding ceremony, wedding arches and wedding cakes make a more than welcome return. There are a few styles of wedding arch, to help you set the perfect scene for your wedding. Of course, when you’re trying to set the perfect scene, you might want to first check that your Sim isn’t due at work, so they don’t change into their work uniform at the altar…

Read more over at BlackGarden, & SteveB