Yeah I was giving young visitors to my observatory a sky tour Monday night and when I was explaining that the light from NGC 253 that was entering their eye had been travelling for 11.5 Million years to get to the eyepiece, one little girl, about 8years old, piped up and said "was that before baby Jesus?" and I said "oh yep, even before Adam and Eve!" she said "Woooow"
As for preschoolers ie under 5, I dunno
probably some quirky sand pit or lego analogy that will create a picture, I always like analogies to help explain concepts in astronomy, just need to pick the right one for the age, sex and the person.
Mike