I'd suggest getting a new model (something that released in 2016), so that it will likely get updated to Android 7 (it has a dual screen feature-ideal for tabs), at your price range you will only get Android. If I were you I'd wait because Google might announce one soon, but it may be over your budget.
Alternatively just look on argos, I was on there a few days ago and came across some good 10" ones for less than £150 with 7" going for even lower.