A newlywed welcome home from Aus!

Our brother recently got married in Aus and lives out there. We couldn't attend as we're both students and one of my sons is autistic and so would not have coped with a day of travelling. Him and his wife and their two children are coming back to the UK either end of this year or beginning of 2015 for a visit and a post wedding celebration. We would love to hire a flash mob to welcome them at Heathrow airport. Their wedding song was Passenger Home so we thought that could be incorporated somehow. We really just need an idea of price etc.