My husband, being off sick from work, has been accompanying daughter to school, she is six. She is close to a Muslim girl who I will call Kay, and they really want to see each other outside school, for tea, for weekend play dates etc. They met at school and have been friends for nearly two years. Kay rarely goes to any parties or events outside school hours. 
Kay's mum is a British Muslim. My husband has attempted to be friendly towards her and asked if Kay would like to come for tea, but Kay's mum refuses to talk to him. I think this may be due to our cultural differences and I think its such a shame. 
We are a liberal family, everyone is welcome in our home, whatever heritage or religion, sexual preference, whatever, and we do not want to stifle any of my child's friendships. If I could take dd to school and talk to kay's mum I would, but I work such funny hours. The girls get so excited making plans, but as parents, we feel we cannot help dd realise her plans. Dd has other friends of other backgrounds but we haven't encountered any problems before.
Sorry to go on but has anyone else had dc who wants to mix with children of different heritages and religions but barriers have been put in the way?