Here's a quickly made ePub with an SVG version of
Charis SIL embedded. The XHTML/CSS works fine in Chromium, which is webkit based, like Safari. (I'm using linux, so I can't test even on Desktop Safari myself, much less an iPad.) I'd hope it would work if anything would.
I guess I should have chosen a more distinctive font, but I'm too lazy to change it now. Very interested to see if this will work in iBooks.