three
You can take as many as you wish as long as you pay the extra for the transportation
10
50 Pounds or 23 kilo
2 suitcases are allowed in an airplane
The Franks and the Van Daans did not carry suitcases to their hiding place because they did not want to draw attention and suspicion. Instead they wore as many layers of clothing as possible.
The answer depends on the volume of the individual suitcases. Also, because they are rigid, it also depends on the dimensions of the suitcases.
There are many places whee one can purchase suitcases for traveling. One can purchase suitcases for traveling at popular stores such as Walmart, Target, and Macy's.
Cheap kid suitcases can be found on many sites on the internet. You may want to try eBay or Amazon and broaden your search by maybe only searching for "Suitcases".
Suitcases come in various sizes therefor it would depend on their sizes.
They did not take suitcases into hiding - a Jew on the street carrying a suitcase was instantly suspect. Miep and Jan Gies carried as much of their clothing with them under their raincoats as possible, and when they left home to go to the annex, they wore many layers of clothing under their coats.
Purchasing children's suitcases (or just suitcases in general) can be done in many different places. You typical mall should have them. Amazon is also a great place to shop if you wish to do so online!