First, be aware that any stream technology using Adobe Flash will not work on the ipad. Most Java-based sites work fine, a few don't.
The amount of data coming across in a stream of ticker quotes and charts is very low, as it is usually text and numeric data that gets sent, rather than graphics, and the local hardware computed the data into graphics.
So I would guess it might work just fine and not be a data hog, but you would have to test it yourself.
If your sites open on an iphone, they would work fine on the ipad.
If in doubt, got to an Apple store or find a friend with an ipad and try out your sites, to see how they look.
I use the ipad to follow ihub boards and trade through my Schwab account with no problem.
The real bandwidth hogs are streamed video or music. Anything based simply on updating text or numbers is not going to be any problem.