Avoid any soap or lotion that contains perfume or dye. Sun also irritates it so put on sunscreen and wear a hat or cover up skin, if it's not too hot. Bathe him only every 2 or three days. Just wash hands, face and diaper area in between. Try cool or room temperature water, it's less drying than hot water. Dry the skin thoroughly after a bath. Aveeno and Aquaphor are good moisturizers to use. Use light, breathable fabrics like cotton.
As a parent and grandparent, bathing is very important and bathing daily does not hurt-in fact, it is recommended to bathe them 2ce a day if possible-minus soap and harsh detergents. Also, it is very important not to completely dry them-moisture is a important ingredient in treating eczema. You don't want them too wet but wet(damp) enough to allow moisturizers to soak into the skin.