I think easytether and PDANet only support Ad-Hoc, I'm not 100% sure on that though. Both of those are a one time pay app. One (or maybe both) have a limited free version, so you can try it out and see if that works for you. I've got no clue if the iPad supports Ad-Hoc networking, so I'd start with a free version.
If it doesn't, the Verizon mobile hotspot app it your only non-rooted choice since that should let your phone broadast a true wireless access point, not Ad-Hoc. But that tacks on the extra monthy fee Micah pointed out.