My son has been going to Halifax Karate Center for almost a year now.  The place is just wonderful for kids.  The owner Rich is a great guy and the kids love him.  He's really big on building self esteem and really knows how to handle the kids.  The prices for his studio are very competitve and the kids are allowed to go up to 3 times a week.  I highly recommend this place for kids if you're looking at karate places in the Halifax/Carver/Plympton/Pembroke/Kingston area.