As TCL-Mumping states, there's no direct correlation between grams per square metre and tog ratings.
This page is unrelated to toddler's bedding but it's good enough to confirm my belief that 100gsm would be at the lower end of the tog scale:
http://www.peacetoget...e=37220&idDetails=167
That's probably as it should be, since duvets for children should have lower tog ratings than for adults. This is taken from the John Lewis website:
"When choosing a full-sized duvet for a child, unless their bedroom is very cold, it's best to stick with a lighter weight duvet between 4.5 and 9 tog. As children are smaller it means that their duvet traps more air and increases the level of warmth over and above that experienced by most adults. A heavier 13.5 tog duvet may well prove uncomfortable, and is not recommended".
Chris