With the big meals, it seems you are saying those are potluck meals. So your friends probably already are planning on bringing something for those ones. Since a potluck is everyone bring something. I don't think it would be rude to ask at all what others are bringing. you could send out an email now, since it's about 2 weeks away, and ask them. And tell everyone you want to know, to make sure that there is all types of food going to be there. you don't want everyone showing up with chips, or a dessert. So you can tell them, you want to make sure, there are chips, dessert main dishes, salads, rolls. IF they are at your house, you can decide, if you will supply the main foods, and others to bring sides, or how you are going to do it. And if you are supplying the main meals, you tell them that as well. you might have someone offer to just give you a few dollars to help with the cost of the main dish, instead of them bringing something.
Even traveling from ohio, they could bring chips, or desserts, or some sides that don't need to be refrigerated.
I would definatly let your friend know that you do shopping on what day, and ask her if she needs you to pick up anything for her, or tell her that you guys will go shopping friday morning, to get everything you need. Then she can get what she needs for herself, and son.