The menu sounds great. I'd suggest maybe laying out extra chicken or making an extra ziti that you could heat up if you need it, or otherwise freeze for another time, that way you have an option to add more if you underestimate. Instead of chicken breasts, if money is tight, a whole roasted chicken or turkey breast for that people can carve off of is quite inexpensive and looks great. For the chicken breasts, I'd consider at least two pieces per person (2/3 of a breast), and for a small, appetizer size meatball, at least 3 or 4 per person. I'd place the ziti very prominently on the table to encourage people to consume it since it is likely the least expensive main course.
For wine, I'd definitely check Costco. The one near me has ratings on the wines and the prices are really good compared to other stores. They also seem to have the full range of prices from very inexpensive to high end, so you can probably find a good one to suit your budget. Most people I know prefer red, but it might be different for you. A non-grape based wine can be great, but is a very specific taste, so it's hard to predict how that will work with a large group.