DS download play - multiplayer from one cart - which are best?

[InvisibleKid]

The wife and I are going on holiday next week - what games are great for playing multiplayer from one cartridge?
She's awful at games and has really enjoying Layton and puzzle games - so I want those kind of suggestions really..

Any ideas guys?

Thanks in advance for the help!

[Neon Ignition]

Mario Kart DS will probably be a popular choice, though Player 2 can only have the default character