Best thing to do is call Verizon and ask. I'm pretty sure you can activate it on any line you want, since you'll be receiving it in the mail unactivated.
But yes when you order it, you'll have to add the $29.99 data package to his line along with the phone. However, I think his does not go into effect until you actually activate the phone. So if you just activate the phone on our line instead, and immediately cancel the data plan from his line, you should be fine.
Again, call customer service and ask what to do. They're usually very helpful.