My 4.5-year-old and 1.5-year-old went to my mother's, their beloved grandmother's, memorial service at church. 1.5 was so young she didn't understand what was going on, of course.
I think any decision someone wants to make about their 4-year-old is fine. But I would encourage any parent not to make the decision primarily for the purpose that you don't want to explain death or related concepts to them. It is not an easy thing to explain death to a child, but I don't think it helps you or them to try to avoid having the conversation just because it's a difficult one. I don't know how good a job my wife and did with those conversations with the 4.5-year-old - and those conversations continued for months and years afterwards, because she would continue to randomly bring it up from time to time - but we would have had to have those conversations anyway, it's not like we could just pretend like her grandmother was still alive.