I have same problem. I think your rear derailleur will handle 29 easily, and most likely 30. But man that 30 Campy is hard to find in USA. Seems plenty in UK but not in USA. I just found one in Canada and it's in the way. Had I not found it, I would have gone with the 29 which is readily available.
But I have a question - you're running a Shimano crank on your Campy 10 speed? Does that work ok? I'd love to goto a 46-30 in front, but I'd need to goto Shimano, FSA, or SRAM.