When we lived in Idaho we were exactly two hours from our driveway to the West Yellowstone entrance. We often put the kids and picnic lunches in the car and had Saturday adventures there. Those picnics often ended up in the car though because of unpredictable weather. It was still fun anyway.
Sometimes we explored different areas of the park and sometimes we just hung out at Old Faithful, settled down in the rocking chairs near the fireplace, and ate ice cream while waiting for the geyser again.That's not a bad way to spend a lazy Saturday.