Well for him to even utter the word Pentasa it is a little encouraging. Disease must be mild and may be isolated to the colon as Pentasa has a better success rate with colonic only involvement.
It she has disease anywhere else, I would be asking for him to justify Pentasa and give you a clear plan of how long you are going to give it to work (after the steroids are stopped) and what the exit plan will be.
Mild disease doesn't always respond to mild drugs...ask me how I know. So while I agree to go ahead and try mild drugs on mild disease, it is good to define what success should look like, what he will be using to measure success and when you should abandon therapy.