Does he take things from the children, e.g. food or treats intended for them? Is he cavalier with things and breaks them?
If he’s also like this with the children, then he’s ‘king of his own dung-heap’ and telling you all so.
Also, regarding the children he’s not modelling good behaviour if he lies and hides and steals stuff. So the problem spirals if that’s what they’re seeing.
Do you have joint finances and does he spend on ‘his’ stuff from your communal pot leaving you short, or leaving you to pay all the bills leaving him free to buy the fun stuff, or do you have separate finances?
Financially, I’d be concerned he was fiddling taxes etc, or not paying bills, if he was that inclined to lie, hide and steal. Or worse, laying away money so you can’t get at it.
He’s not a good husband and father if he lies to his own wife and children even about small stuff. I’d wonder what bigger lies were being told.