So, symbol of healing says it works similarly to symbol of death. I'm considering allowing you to "only include" people attuned to the symbol, similarly to how symbol of death allows you to exclude attuned people from it. Would you guys allow this?
Symbol of Healing: "This spell functions as symbol of death, except..."
Everything after the "except" applies, regardless of what symbol of death would do. That includes having all creatures within 60 feet being bathed in positive energy.
I don't really see a problem with changing that as a house rule, though.