Do your children pronounce any words differently to you?
Of course if one parent is foreign this will have an influence, but have you noticed a different accent amongst children, where both parents are British?
In London, many youngsters are growing up talking in an urban dialect but have you spotted any influence of American TV shows/Youtube?
I have noticed children are pronouncing "thank you" like "thenk you" and exclaiming the word 'what!' sounds like waht rather than woht