He was arrested, so the arrest could show up. He was charged, so the charge and its disposition (even a dismissal or acquittal) could show up. How he might remove the information from his record depends on the disposition - there's a lot of information about Illinois expungement here.

On a peripheral issue, he hit you. If it's the first time, it probably won't be the last. Domestic violence usually escalates over time, with the "honeymoon periods" when he's sweet and promises that it will never happen again becoming shorter with each new incident. If this is truly the first time he has hit you, I would suggest you consider if you really want to stay with him - and if you decide to stay you should make clear that you're out the door with the kids if it happens again. If it is not the first time, you need to start thinking about the effect on your kids.