regarding the dont eat in front of your child part, what my mum tells me is, dont let your child watch ppl eat bcos it is plainly rude n it will become a habit. another thing is, when your child is looking at you eat, offer him some,if they r not at the right age of eating, dont eat infront of them since you r not offering them. this is becos when your child keep seeing you eat, then they cant get to eat, they will become very "gian" to eat, and it goes back to the first reason, they will form a habit of staring at other ppl eat. not become greedy. i dont know what other ppl's mum or inlaws tell them but this is what my mum tells me n i think it makes sense, so i do not allow my child to look at other ppl eat, and if im eating and she wants some, i will offer her. things that i do not wish to let her try yet, i will not eat in front of her.
as for old wives' tales. things that i think make sense, i will just close on eye n follow, things that are totally ridiculous, i wont follow.