Re: different cultures, religions, naitonalities?
Kids are going to learn English anyway outside the home, if parents are serious about their Pakistani identity and maintaining links with back home they should teach their kids Urdu.
In our house we always spoke Urdu and the English I learnt was all at school/friends/TV, I still remember I had a few problems communicating in the first year or so of nursery but it was nothing major, today I speak both accentless English and Urdu.
I think every Pakistani Muslim should know Urdu, Arabic and English, other languages are a bonus.