Marion/Mullins is rural and poor. I don't much else. I grew up in nearby Florence 25+ years ago, so my knowledge of the area is both indirect and dated. I don't know about the schools and I don't want to speculate. However, I'm comfortable saying that your educational choices would be limited.
The towns are about halfway between Florence and Myrtle Beach -- about 40 miles from each. Depending on your desire for entertainment, you might spend some time traveling to these bigger towns. I guess that's what you could use the Harley's for.
In the summer, it is hot and humid. Very humid? Less humid than Charleston, but there are summer days that the air feels thick.
There isn't too much paddling going on anymore. I received a few licks in my day, but no kids gets paddled where I live on the other side of the state.
Well, hopefully a Mullins booster will pitch in with more specifics. Regardless, please visit if you can before moving down.