This is probably too late, since it is evening now.
I'd bet your kids go to Northside schools. I teach in Northside. I was there until about 6:20 this evening trying to get my room ready for Monday. It doesn't look promising thus far.
Our open house isn't until after school starts, so I've never gotten one of these gifts. Since you don't know what she/he might need, I could only suggest some sort of cutesy trinket.