When my child started eating solids I noticed then what hand she preferred using, but it wasn’t until she started writing that I was certain.
My child and I are both left-handed and we both eat using our right hands. But read below:
“This applies if one is able to eat with the right hand. But if one is unable to do so, there is no sin in that. Al-Nawawi said in Sharh Muslim (13/191): The objection to eating and drinking with the left hand applies so long as there is no excuse. If there is an excuse which prevents one from eating and drinking with the right hand because of sickness, injury etc, then it is not makrooh.”
Islam Question and Answer - The reason why the right hand is preferred over the left