A few years ago when there was only two of these boys I had them for over two weeks while their parents traveled through Europe on business and pleasure. In an effort to make their stay more memorable and fun I planned our own activities at home to correlate with mommy and daddy's travel itinerary.
Ahead of time, I went to the library and checked out books from the children's section on the locations and the landmarks that the parents planned to visit. This gave me great pictures and simple wording to share with them. I had prepared projects and activities that related to the place where mommy and daddy were. I included the animals, the foods, and the special things to that culture that would interest a child.
I placed a world map on my fridge and used yarn and a magnet airplane and train to show the travel routes and the current destination. Since it was a long stay I created a countdown chain made of construction paper to help them count the days until mommy and daddy returned.
I shared some great learning and bonding times with my grandsons and once the parents were home and spoke of and shared pictures of the places they had been the children were familiar with many of them. The gifts brought back were also meaningful to the little guys because they too had traveled the same route through pictures, words, and activities at home with grandma.