The minigames exclusive to the DS version are five-minute distractions at best, just like the rest of the minigames. The best of them, Bomb All Together, throws waves of zombies at you and gives a limited supply of bomb-type plants to deal with them. The lamest, Heat Wave, has you slide around limited plants and (sigh) shout at the microphone to inspire them to greater heights of zombie ownage. Even so, they're not worth much entertainment in aggregate, as the strength of PvZ has always been in the core gameplay, not gimmicky one-off scenarios.
Plants vs. Zombies is a great game, but explore your options before committing to this version of it.