Jennifer,
It's one thing to do pomanders for hanging on pews, totally another for little girls to carry. The foam can easily break up not to mention they will be awfully heavy. My suggestion would be to make tulle puffs and then glue the carns in, or a ball of bb with the carns again glued in.
If you DO decide you want a water source or the bride does not want anything but a smooth ball, you can use the small igloo so that there is a cage around it. It's going to take close to 2 dozen carns for that, MAKE SURE YOU USE BOUQUET HOLD or FLOR-LOCK!
The other thing I've seen done is using the netting sock that comes on spiders. You slip your piece of foam into it and tightly tie off both ends, then soak it. This gives something more stable to hold the flowers and you can more easily attach a loop for the handle and also a tassel if you want.
hth
For pricing I would say about $50 each.