I totally agree w/the others about the lasagna or any Italian casserole like baked ziti or manicotti for that matter. Easy to prepare in advance and a real crowd pleaser. If you are wanting to elaborate on the Italian theme Sausage and Pepper goes really well with it as well and can be prepared on the grill(a bonus, you can delegate this to DH if he happens to be the griller). I am from NYC where entertaining Italian style is just the norm and this combo is really popular. Throw together a nice salad, some bread maybe a couple of apps(maybe some guests will offer to bring a few) and it is quite a stress free feast.
PS-Lucky you to be hosting so much family. That is so much fun!