Right.
OP I have spent the last 30 years in zone 2 London and the last 6 months in zone 3. SW so close to Surrey. Sutton is not majority ethnic although it is more diverse than, say, Cheam, Epsom, Carshalton, etc., but not nearly as diverse at Croydon/Mitcham which still are not majority ethnic.
Second point of fact Eastern Europeans are far more matter of fact about children sorting things out amongst themselves, learning to laugh off a graze or scrape, and generally developing a bit of "toughness" - no Eastern European blood in me - oh no 
Third point, where I live most of the Asians are quite openly moaning about the Poles/Eastern Europeans and the Asian gentleman who owns most of the shops locally now employs the Poles almost exclusively because by his own admission they work harder than his his nephews and nieces who have become entitled like the Brits.
Fourth point, if you don't like Sutton any more, move. I wouldn't live in Sutton because when I've gone to the shops there I haven't liked a lot of the people there mostly indigenous whites
Fifth point - if you don't like the playground you've been playing in, find another one; likewise soft play centre. All playgrounds have dc who play there regularly; all parents and children like some more than others.
Sixth point - Belt up.