Provided the kennels are happy with this and the owner is in agreement, I really don't think it will have any effect on the dog other than he will get more exercise and attention on those days. Once the first visit/return is over he will soon realise he has not been abandoned (although I don't believe dogs think like that anyway). As said above, please ensure the safety of the dog while away from the kennels, as many dogs go missing when being 'looked after' by friends or family.