I understand now.
That is terrible (of course). How old is the eldest child? You say she's of school age. My idea here (I'm not a cop, not in CPS) is to see if you can appeal to them -- somehow -- to take in the eldest so she can have regular meals and go to school.
The parents may even be mentally ill (and I'm no doctor, either).
But at least when they call you to order pizza, you've got a clue as to where they are. You've got more than one phone in your home, yes? As in, a land line and a cell phone, or more than one cell phone? Then when the call comes in begging for pizza, you'll need to have an address for it to be delivered to. With the other phone, have someone (your spouse, if applicable, for instance) call the cops and tell them a child abuser/vagrant is going to be at such and such address. The police may or may not act but that's something. It will also be the start of establishing a record.
Contact the cops in Wheeling (or wherever) enough times, there will be a file opened up. Explain the situation just as you've explained it here. You feel the children are being neglected, possibly abused, and certainly being denied their right to an education. Call several times if you have to, both CPS and the cops.
I'm sorry it's all on you; I really am. But if you really want to help the kids, just one anonymous tip is probably not going to be enough.