Are they fighting in a desert or something? Gaara may not have enough sand to tackle the team and defend himself. Robin could even break his back using sprouting hands from his knees.
Kakashi won't use kamui in every single one of them and most of them pack enough power to deal damage to the other team.
Every single member of the Strawhat Crew have durability way above whatever the ninjas can dole out. Yes, even Usopp, as crazy as that sounds.
Gaara can try the sand trick, but the minute the wave shows up the Crew will take action. Nami would probably use the climatact to blast a hole through it to keep the crew clear, then Luffy, Zolo, and Sanji go to town.
I know genjutsu wouldn't affect the smart ones like Zoro or Robin, but even then it takes at least a few seconds to recognize one, in which time the ninja's would be able to do something at least. But still a lot of this depends on the area and how well the ninja's plan is. Kakashi is smart so their strategy would be decent enough but if the area isn't well suited, pirates take this.
A beach? Well that's pretty much the perfect area for the ninja in this fight. Water walking Jesus ninja vs characters who can't swim. Not to mention Gaara gets sand. No, more ninja really aren't necessary if you give them a sneak attack, though personally I'd add one just because the shinobi work in groups of 4.
Though this area does effectively cut the ninja's strength in half as both Rock lee and Kakashi would be distracted by Nami and Robin's breasts.