Just to be sure,
Can I download games that I buy from the shopping channel to the same sd card that have the homebrew channel stuff on it without altering or earasing the homebrew data?
I've never tried with material downloaded from the shop channel, myself, but I assume it's akin to moving other savegames/channels over to the sd card. And that's perfectly fine with homebrew loaded on, so I presume the answer is yes.
"I think that the Wii is a beautiful piece of hardware, and a broken Wii is a tragedy. It doesn’t matter why or how." -- Bushing