First of all, I'm moving this to manga, where it should be.

Secondly, are you up to date with the newest manga chapter?

It is basically admitted that Tsunade made an alliance with the Sand trio specifically for that purpose...she hints as much to Raido and Genma in the hospital, and the Sand trio identify themselves as the allies of Konoha.

I think Tsunade is stuck between a rock and a hard place: she can't afford to let Orochimaru get hold of the Sharingan, but all her chuunin and jounin are already out on other missions or injured. The only option she has is to place Naruto and the others in harm's way; she knows Naruto's potential personally, and Shikamaru and the others are the best choices she has given what the situation is.