You know how everyone has been complaining about the Sims 4 being too easy? I think the developers listened to us. There are some bugs, definitely, but also this is a complicated event to arrange. After 3 weddings, none with mods, all using the new pack, here are some strategies:
If you want to use the wedding venues that came with the pack, go into build/buy beforehand. You need to make sure there is only one wedding arch and one aisle in the venue. I would also suggest adding a kitchen counter in the dining area. My Sims' wedding cake didn't show up, and it might have been because there was nowhere to put it. Also, I didn't see a stereo anywhere in the venue I was using, so I added one.
You can't have a club gathering at a wedding venue, so the only way to make sure that everyone is dressed in formal clothing is to make all the guests and wedding party members of your household. You will have to change outfits for each of them. I'm pretty sure this is a bug, though, and have hopes that it will be fixed. Right now, if you check "Polished" for guests when planning the wedding, they still show up in everyday clothing.
About the cake:
1. Have the Sim who is planning the wedding purchase the cake just before going home.
2. At home, put the cake on the counter and select a topping for it.
3. Click on the cake and choose "Select as wedding cake." It will disappear and reappear at the wedding venue if there's a place for it.
4. Check your wedding plan. If the cake shows up on the same screen as the one showing the outfits, it should show up at the wedding.
About spoilage -- before the wedding starts, mouse over your cake and see how long it has. If it's only a few hours, go ahead and cut the cake first. This might be another bug that will be fixed. I did actually have success with a cake, but it was the $15 white one that my Sim made.
As several people have suggested, forming a group after the exchange of vows is the way to go. Use "go here as group" to take them to the champagne bucket for a toast and to get close to the stereo to dance.
I don't know how long it takes for the bride to throw her bouquet, but the command is on the bouquet. I got tired of waiting (and so did the hopeful Sims gathered behind my bride). Hopefully, this is another bug that will be fixed.
It might help to regard yourself as the director of a cast of thousands (or maybe some cats that need to be herded) rather than an audience of your Sims. All in all, I have been having fun with this, even with the one where some stray elder showing up at the wedding afterwards died.
