The Uncertainty Principle in Particle Physics

The size of an electron can be almost anything. It depends on the uncertainty principle. If you know everything about its velocity, then its packet is infinitely wide. So that's intellectually not that satisfying either. But what if you assume an electron is just standing still? Like when you're trying to measure your kid how tall they are and it's impossible because they keep moving. What would that happen? Would you be able to then get a pretty accurate size?