I've been a funeral singer for many years. There are really so many but these are the top 10 in my experience: Ave Maria (Schubert), On Eagle's Wings (Joncas), Be Not Afraid (Dufford), Time to Say Good-bye (sung by Andrea Bocelli), Morning Has Broken (hymn - but also performed by Cat Stevens), You Raise Me Up, Wind Beneath My Wings, Celtic Song of Farewell (Londonderry Air), Amazing Grace, Lord of the Dance (hymn).
I've even sung My Way by Sinatra - and the Canadian National Anthem. That being said, funeral songs are personalized to memories of the family and what mom loved to listen to. If this is a church service then ask to speak to the Music Director. A funeral director will also have a list of musicians who can help in the direction of a Mass or Memorial Service. Let them help you - they do this for a living. As a grieving family member, there are so many other things that you need to take care of.