Hey matty, Pentasa isn't a very effective medication. It works for some Crohn's patients, but not for many.
Entocort should work on the ileum (it doesn't work for the upper smaller intestine and lower colon), but isn't a long term medication in any event.
As people have said above, "mild" is just a classification that some docs use and doesn't really mean that much. When I was diagnosed in 1999, one of the two GIs I originally talked to classified my Crohn's as "mild" too, I took Pentasa for 4 years and it really didn't help at all (but at the time I really didn't want to deal with Crohn's, which wasn't a smart idea).
Anyway, if you got symptoms and you really want to get rid of them and if Pentasa isn't helping, you might consider the standard long term Crohn's meds (aza, 6mp, biologics). Alternatively, if you rather stay away from any drugs at all, you can try to get into remission through diet, sport, stress relief etc. only, but you should remember to monitor your inflammation level - constant inflammation leads to scaring and all kind of problems down the road.