We've been to both and we return to both every trip.
The thing to consider about Teppan Edo is that you are sitting at a counter around a cooktop that reaches 500 degrees-plus. When they refurbished recently, they made the counter wider so you are further away from the grill, but it IS still a danger (it is physically possible to reach out and touch the grill, even for children). The other thing is that you sit in a row (although with your young ones, they'll seat you around one end and a section of the counter). You'll also be sharing your table with other people.
The counter or table is a long rectangle. One long side of the rectangle is where the chef works -- no one sits there. There are two seats at each short end of the rectangle, and then a row of seats along the long side opposite the chef. I'm trying to remember exactly, but the tables seat either 9 or 8 people and they do fill the tables.
If your kids need help (cutting food, dealing with drinks and cutlery, etc.) then it's going to be tricky for you at Teppan Edo. Personally I would go with Le Cell just so that you are all seated at a regular table and you can give your children the help/attention they need, and save Teppan Edo for when they are a little older. Admittedly I have only one child and perhaps I'm showing my "worry-wart" side about managing a larger group, so maybe someone with a family more similar in size and ages to yours can chime in.