Setting aside any emotional opinions on entitlement/NRSA/DYKWIA/babies/PDBs/etc, the correct answer really is this simple. It really is.

Passengers from coach should not enter BE to contact family/friends unless a true EMERGENCY is occurring at which point an FA/pilot should be involved. Changing a diaper isn't an emergency nor is a child vomiting. These are both routine childcare responsibilities, and if both parents feel the need to be present for such events they need to purchase tickets in the same cabin. It would be no different for people traveling with spouses or friends. Outside a true medical emergency I can't think of a situation where contact would be required.

For those who think such a viewpoint is callous and unfriendly, I would question whether they understand the slippery slope of allowing constant visits to another cabin for leisure purposes.