They had to leave the car a ways back. Erik hadn't been best pleased--at not having the solid metal readily to hand, Charles suspected, not because he objected to walking. The mutant they were looking for apparently made his home far off the beaten path, far enough that driving especially close simply wasn't an option. Charles should probably have objected to the walking--his legs wouldn't be thanking him, later--but he was far too excited.
The mutant they're looking for is close now, anyway. Charles can sense him plain as day. He could have called out to him from much further, saved them some walking, but people were generally more receptive when not surprised by voices in their heads.