No, definitely not at the experential level of a 5-yr-old. They enjoy the outcomes of math and science, like eating the M&Ms they jsut counted or seeing an exploding volcano. The act & outputs is mostly beyond their comprehension and boring as hell. Trying to give your preschooler a "head start" in math is sub-optimal at best.
I’d say that doing the fun parts (and what’s fun for them varies with the individual child) will give them enough of a head start compared to children whose parents do nothing of the sort.