Mynxie, I am sorry for your loss.
Of course it is OK to ask for the song to be played at your son's funeral. I am sure that she will understand when you explain.
As sharon103 has mentioned there is a time allocation for a service.
Last year when my DH died, we had a humanist service for him but was able to have two readings, tributes and three songs included into that 30 minute service.
I am sure you will be able to have your special song, you as a mother are not asking for much.
Again so sorry for the loss of your precious boy.
The Israeli election, will Netanyahu stay in power?
Harry wants to reconcile with his family!



