I would agree about transplanting only once. I'm sure you'll want your grand-daughter's project to be successful so you need to be aware that most major varieties are monoecious... meaning, they are self-pollinating. Each plant produces both male and female flowers... but, if your growing the plant indoors, then you'll have to help nature along since the plant requires insects for normal pollinization.
Fairly easy, but you'll have to learn the difference between the male and female flowers. The females will have what looks like a baby, spiky cucumber immediately behind the base of the flower whcih the male will not have. Use a small (clean) paint brush (or even a Q'tip in a pinch). Brush the inside of the male flower by twisting the small brush around, then brush that inside of the female flower. Some use the technique of pulling all the petals off the male flower and then stick the remaining part inside the female and twist it around.
Luck!