Gosh, I must have been an awful mother for leaving my children with my parents for a week while hubby and I went skiing! First it was just eldest son, when aged 6 months, 18 months and 2 1/2. Then it was son aged 3 1/2 and daughter aged 6 months. The following year my parents drew the line at having another baby so we took the 4 year old with us and left the other two babies. And to add to the horror, our 4 year old went to ski school every morning!
We did then have a couple of years without skiing until all three children were old enough to come with us but my parents would still have been willing to have them stay with them two at a time. My parents were only in their 50s so fit enough to enjoy running around after young children and my brother and sister were around to help out.
I don’t see anything wrong with enjoying time with just one child, my eldest some was often taken out on his own while the babies were at home to give him some special attention.