Darth - I am very sorry for your loss. With dementia the loss happens twice, once when the loved one loses their mental faculties and then again at death. Please take the time to grieve and remember your mom as she was before the dementia took her from you. It will be stressful engaging with the congregation and with family. In our experience, at funerals some of the usual witness stuff takes a back seat to the issue at hand. I hope that is the case for you.
All the best,
z