T.S.
I agree. More pasta. It's the most filling part of the meal, and this may be the first, not third, meal several of the diners are eating today, so you want to have plenty. Also, pasta is cheap, so if some goes to waste, so be it... although I'm sure you'll find SOMEONE willing to have seconds :)
Similarly, if you can easily stretch the sauce now, I'd do it. You can always bring extra home. If you end up having to pop open the jars mid meal, don't stress. I'm sure everyone will really enjoy the dinner no matter how it comes together!
T.