Hans, your question is an important one, especially now given the Covid-19 pandemic. Before the pandemic, we helped take care of our grandchildren even if they were sick. As a result, we often caught their colds and got sick ourselves, but we weren't afraid of my having an episode of SCLS because my full dose (2 gr/kg/month) of IVIG had always protected me.
In the meantime, my older brother (he is 77 years old) and his wife, who are both retired physicians and they don't have any serious, underlying medical condition -- never mind SCLS -- had a policy that they would not visit or host their grandchildren if they had a cold or other sickness.
But then in January my wife came down with Influenza A and she gave it to me, though it was not the fault of our grandchildren, and even though we both had been vaccinated against the flu, but this time it triggered my first episode of SCLS in more than 10 years, see https://rareshare.org/topics/1967 Therefore, even if there was no Covid-19 pandemic, now we would probably not see our grandchildren if they were sick.
One of the few good things that have come out of the pandemic is that during these months of strict isolation, our grandchildren have not been sick, because they have not been playing with other children. Therefore, we have spent a lot of time with them and we have also not come down with any sicknesses. We have enjoyed this togetherness very much.
The dilemma we face is what are we going to do, as a family, if schools reopen in a month's time, even if for two days a week, rotating smaller groups of children so that they can keep their distance from other children? Will our grandchildren start to pick up colds and other childhood illnesses once again -- never mind Covid-19 -- despite the best efforts of schools and parents? Should we stop seeing them for a month or two, until we see what happens? It is a very tough decision.
I don't know about you, but spending time with our grandchildren keeps me motivated to live on.