It takes shorter. Think of it this way: everything around them Lorentz contracts (from their POV). Since velocity is unchanged, it takes a shorter time to move the distance.
I think you mean that the ship appears to undergo Lorentz Contraction to hus-bot. From the kids on the ship's point of view, everything else has expanded, so it would take longer for them to travel the distance, but only from their perspective.
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