xenophon41 is right about the middle part.
: goes back to add another footnote to an unpublishable thesis on information theory :
Respond So Very Promptly
If you can cope with 50 people, you have a huge apartment. Not replying is very rude. You’ve had twelve people say they are coming, so plan for twelve. If more show up with food, fine; if they show up without, politely turn them away saying that they didn’t let you know.
I don’t have a huge apartment, but I never expected 50 people to show. If they do, they will have to hang out in my huge backyard, although it will probably be a tad chilly for that (around 35-40 degrees (Fahrenheit) tomorrow night, if the forecast holds).
Nope – they’re planning to just pick up a sub at Quizno’s. 
Reply Soon Very Politely
As I mentioned earlier in this thread, tomorrow I have planned my 4 year old’s birthday party.
Not only have fewer than half of the people responded, I got this charming phone call tonight. “I just wanted to let you know I cant commit. We have to run some errands and we might make and we might not, I just can’t say for sure.”
Well, that’s helpful.
So this lady and her 4 children might be coming. I might need party hats, food, cake, and goody bags for them. Or maybe not. She just can’t commit.
:rolleyeyes