ummmm I feel for you, one of mine went missing for a while, he'd been nosing in a shed and got shut in. Make up some posters and stick them up in your street if he doesn't come back tomorrow. Notify the vets around you in case someone finds him and brings him in, and also if you have a local cat refuge (Cats Protection etc) let them know. It might be that he ran out when the kids were with you - mine run a mile any time they hear children, and if he's not used to going out much then he might have panicked and be hiding somewhere until it gets dark, then he'll try to find his way home - I hope so, very much. At least you have chipped him so the vets will know who he belongs to. I feel for you - let us know what happens.