Praying at a government function also does not force you to participate. Again, the majority rules only apply when it supports your position.
It all depends on who is doing the praying. As long as it is not the Government sanctioning and endorsing the prayer and it is simply a citizen doing the praying it should be legal in the US to pray at an government function.
And while you are right, a lot of Christians would get their feathers ruffled by an Imam opening a governmental function I think it would be great.
The National Cathedral in DC often has clerics from other faiths not just attend but rather perform services, give talks and lectures and teach classes on their religion.
Anyone so limited that they can only spell a word one way is severely handicapped!