|Biff, I'd recommend the softest and biggest wheels you can attach to the skates under consideration. I ride 78a on my street skates, it would be difficult to get anything softer. There where rumours about 74a inline skate wheels back in the times, but I was never able to get hold of them. Apart from that, the wheels on my street skate aren't that big and they are pretty roughed up too. I should get some now street wheels.
BTW, you mentioned that Alex has some pretty small wheels on his ramp skates. I have given him my set of Autobahn wheels which I had lying around since about a year or so. Better he uses them than me having them lie around.