Two points here,

1) There is no way of telling this far out what aircraft you will get. Even in the last few days, it can still change and the airline are not under any obligation to give you a specfic seat type.

2) The TG fully flat seat on the BKK-CDG route is NOT suitable for travelling with small children, as it is a herring bone layout. It is designed for the single traveller who wants privacy.