In addition to prex's recommendations: Make two stacks of magnets, one with North pole up, the other with South pole up. Bring them together (carefully) so the North & South poles attract (you can add a non-magnetic spacer so the end-user can pull them apart). A substantial portion of the magnetic field will travel to the neighboring stack of magnets instead of out of the box/crate.
If you try this, it's very important for the stacks to have the same number of magnets. If one stack is longer by one magnet, lots of extra flux will travel out of the box.
If the quantity of magnets is large and two stacks is unwieldy, make 4, 6, 8, etc. stacks and stick them together (magnetically). It's important for each stack to have a neighbor.
Also, prex mentioned this but it is worth repeating: There are strict aviation regulations regarding shipping magnets by air. Each box must be tested for stray flux.
Mike