When Clancy sneaks downstairs to sneak out of house - it must be fairly late at night already. Only after are the parents kidnapped, taken to the cabin - heist is then planned and only then do they go to the gala event which is just beginning. This must of been one very long evening to all happen during this time line.
Lewis comments that Wolf Spiders are "one of the most poisonous in the world." Wolf Spiders are not poisonous to humans, as implied by the comment.
There is no explanation how the jewel thief sister escapes from the handcuffs that the children leave her in.
There is, of course, no 199 Fayette Street in Boston. It is a short residential street where the highest street number is 34.
After the kidnappers reach the cabin in the woods, Baxter is never seen of again. He just disappears from the plot and story as if he never was.
There is no explanation why the mother would have a lock up filled with several million dollars worth of advanced CIA technology and a super-expensive car.
Contrary to the claim that the children's journey to track down their mother was utterly pointless, the children had no idea that their mother was quite capable of defending herself against her kidnappers, so their journey was undertaken for very good reasons.
There is no reason why the gift store by the pier would be unmanned and wide open when people are walking past.
When the family try to pursue Leo in a car chase, Leo has a 41 second head start and is driving a sports car at a considerable speed, yet they manage to catch up with him driving a 4x4 slowly within 10 seconds. During the car chase as well, it is hard to see why Leo, driving a fast sports car cannot easily outrun a heavily loaded 4x4.
At 0:17:58 -Clancy doesn't actually bite the cupcake.
Everyone gets into a van to chase the other thieves down. Why did the children need to come? It put them in danger. The police would have momentarily arrived.