@Ty***
, IF you check in and can board your your flight here you will not be questioned by passport control stamping into the country.
It's the airlines that ask for proof of onward travel when flying in on a visa exempt entry because if you're denied entry they have to lug you back on their dime. Still seeing as YOU (the parents) will have valid visas I think the airline isn't going to say anything to you about the children.