If you're getting HIDs for the lowbeams, the foglights will be nearly useless with halogens. The foglights aren't designed to project light very much farther. There's a member here (don't recall his name) that has HIDs in his 2006 for lowbeams and fogs.
I would watch for glare. Glare is usually horrible with halogen reflectors, less with halogen projectors--but not eliminated. Do a search for member lawwailok's threads, he has the shield/squirrel finder mod and now a retrofit.
My recommendation would be install HIDs in your low beams first and go from there. You may find that lowbeams suffice with HIDs. I don't use the fogs at all and find them just for the "look" factor when they are on.
FYI, installing HIDs in any halogen setup is frowned upon because of glare and the optics are not designed for the brighter light output of HIDs. BTW, the proper way to install HIDs in a halogen setup is through a retrofit, which is putting in HID projectors or reflectors in to get the proper beam and cut-off (no glare).