data plan question on bogo droid offer

I was in the vzw store recently and found out that the BOGO droid offer ends sometime around 6/20. One of the reps told me that I could use the offer to get myself a droid and an incredible because they are the same price when it comes to an upgrade.
So my mom and I are due for an upgrade on our family plan, but I know that she won't utilize the $30 data plan. I'm thinking that we could do the BOGO droids, and then sell the motodroid and use the money from that to get her a more suitable phone.
Finally, my question is, Can we cancel the data plan for her line if we get rid of the smartphone and activate a simple talk/text phone for her? I was thinking that there might be a contract on the data plan or something that would force us to continue paying for it even though we're not using it.

TIA,

-KrisPeezy

 

thanks stealthgriffin! that was an awesome quick reply
I just need a few things clarified. So how would it work when I cancel the data plan and switch to the feature phone, will I still be charged for the initial $30 from the data plan therefore the first month? And if so, when is the last possible opportunity I would have before cancelling the plan to get the most bang for my buck?