Alice, until you dig them up and see how the roots have developed, you might want to hold off on planting them in the garden. I am assuming that you potted them up in one gallons pots. I am not sure what you mean size-wise when you say you purchased several babies so can't venture to guess whether they will be mature enough to plant in the garden or if they need more time in their pots. Roots near the bottom holes in the pot would be a good indication that they are ready to plant out. If you knock them out of their pots you will also be able to see if they are ready to plant out.

If you are going to continue to continue growing them out in the pots, then I would definitely pinch them back as they begin to grow to get stockier plants with more vines from the crown. If they are large enough to plant out in the garden, then I would hold off until they are going to get planted to trim them back. That will make the transplanting much easier. You might sacrifice blooms this year depending on their pruning group, but the plants will be happier in the long run.