Sea Turtles are usually larger then most Tortoises but that I'm sure is not what you mean. Usually a Tortoise is more likely friendlier then a Turtle for a family pet. But a small child cannot really take care of either efficiently. Both need proper care and there are a lot of variables on home much space and time that you can give to either. If you as a parent are willing to give a lot of time and care, because most children really don't or won't choose to give up that much of their free time. Then it will be OK. Remember both can live a very long time. Neither A Tortoise or Turtle should be held or Cuddled for very long. Its not in their nature. A Cat or fish may be a better choice.