I caught a few moments of this film on broadcast TV here in the UK in the early to mid 90s or so.
I remember that our protagonists were travelling, and their children (white, male and female, 12 years old or so?) discovered two mysterious objects: a toy (teddy bear or something) which would play music, and a can of tinned food. The parents explained that the can was food, and was very valuable.
At the end, our protagonist enters a large, pitch dark underground chamber, guided by a female(?) disembodied voice who narrates the closing scene. She guides him past unseen hazards, warning “On either side there are great holes which would swallow you!”, and at the very end, we are shown flashbacks to contemporary (~90s) city life interspersed with white flashes that are implied to be nuclear warheads exploding.
These are hazy memories, and the brain cells tasked with remembering them are keen to get on with something more productive instead, so please take all of the above with a pinch of salt!