My only sibling died in a water skiing accident almost 12 years ago. People responded in many different ways, so here are my thoughts:
Some people sent cards, and some called. We certainly weren't in phone answering mode, but it still meant a lot to hear people's voices and to know that they cared.
Many took the time to come to the memorial service, and I know that for my parents, and for me, having people we knew there was a gift. For the record, many of them did not know my sister, but they were glad to get to know her, and to support us, through their presence at the service.
A couple of Liz's friends brought over meals that could be frozen. All of my mother's family came to town, so that was a huge blessing. It saved us money and time. Extra meals were frozen for when my mom would need them.
Friends at home gave us a large lilac bush in Liz's memory, and we came home from my mom's to a clean house, a frig full of easy to prepare food, and plenty of emotional support.
Donations to a trust fund for my nephew were appreciated (and often donations to organizations related to the illness or accident are possible.)
Since this family you know is from another faith, I will share this tidbit. I have a family member that is of another faith than ours, and she complained, within earshot of my mother and me, that the service was a bit too Christian for her taste. Remember, the service is for the person who died, not for us as an audience. These comments were not appreciated (to put it mildly!!!)
My sister's death easily took ten years off of each of my parent's lives. It was a terrible shock for them, and it remains a part of the fabric of their being (or did for my father until he passed away in 2001.) As you have an ongoing relationship with this doctor, it is good to remember that. He, most likely, will never be the same. For my parents that meant a lot of positive things, as well as the expected sadness and stress effects.
One of the hardest things to do is relate to someone that is grieving. I had three children that were three years of age and under when my sister died. I had friends that thought I didn't cry enough. Just the idea that there is a right amount of crying to do, or that people should feel comfortable crying in front of certain people, is silly. The only word I have come up with to describe grief is "convoluted". It makes no sense, and sadness comes and goes without warning. My mother just began crying at Christmas two years ago when my daughter got a pair of socks that reminded her of my crazy sister. It took ten years. That's a long time, but that is as fast as my mom could go. I grieve each year at this time, as the anniversary of Liz's death is Aug. 28th. To have someone, even a patient for an eye doctor, that can understand a little bit of that, is a GIFT. The friends that just walked the road with me were more precious than a pile of gold, I assure you.
These are only my reflections from my experience. Everyone is different, and every day can be different and unpredictable for a person in the depths of grief. I made it through my sister's birthday just fine, but had to pull over and sob as an unidentified ambulance drove by. I was as confused as my friends that were trying to help me. Easy answers don't work, because some life experiences just don't make sense. No, it is not a crisis of faith (necessarily), just a natural response to tragedy. Some people said incredibly insensitive things to me, but that's okay. Grief is confusing, for all involved. A lot of elbow room, an occasional card or casserole, and bucket loads of prayer are usually appreciated. Just do the best you can, and most of the time your care and concern will hit the spot.