So if he can remember how to do an enlarging charm he might be able to make them big enough to put on.

The question is, will he come in those robes? Or wear the hideous thing his mum sent? or will he notice Professor Sinistra left some spare school robes in our common room (I reckon he didn't, or he'd be here by now). Or will he sulk in the dorms and stand up his date?

Time will tell, I suppose!