[TOMT] A movie I watched on TV about ~10 years ago
Two children, a boy and a girl, are searching for a very valuable stone to save their family from ruin; they have an amulet that leads to a hiding place; they are pursued by two adult men who also know about the treasure (as far as I remember, they are the ones who want to take the family's house); the men drive a very old car without a roof, which is started with a recoil starter; the atmosphere is dark, not comedic; there are unusual intertwined trees near the house; in the finale, the heroes escape on an old plane found in the same cave where the stone was.