Hokulea,
My wife is a US passport holder and I a UK passport holder. Whenever we travel to the UK we both pass through non-EU passports together, and in the US we both pass through US passports.
Neither country have insisted on us separating for our respective queues. It works out to our benefit usually as non-EU passports is often a quiet queue, as is the US passports queue; especially on more touristy routes. Though Heathrow near the Olympics will be packed regardless...
Hope it's a great vacation.