I haven't nursed a child while I have had my daycare, but I see no issue for you doing so. The kids watch each other have diaper changes, go potty, get undressed/dressed for outdoor water/pool activities so if you are doing something as natural as breastfeeding they may not even notice or care. If you don't make a deal out of it, I don't think they would either though yes, I would be discreet around the older child.