Re: How to invite people I’m already friends with to my parties?

Yes, you're exactly right. When you start a party, an invite is sent to all the people on your friends list. Though it is true that they won't get the invite until they log back into the game. Unfortunately, it doesn't show on the invite how long the party has been going, or what level it's at, so the recipient has no idea if  it's worth going to the party. If it's already reached level 10, most other players are already gone--though their sims are still present--and you probably won't be seen and get stickers. Also, since we are only able to attend 2 parties per day, if your friends have already attended the max number of parties they won't be able to go to yours. I think it would be nice if we could communicate with our friends and let them know things like that.

In-game communication would also allow us to tell people ahead  of time that you'll be throwing a party and when. There is a thread somewhere on this forum that has that function, but that's assuming any of your friends are active and/or regularly check here.

I hope this answers your question and clears up your confusion.