Gideon has a plan that relies on deception, rather than pure force. The idea of getting the Lamanites drunk will appear again as a ruse in the Book of Mormon. It appears to be a temptation to which they were susceptible. In later Aztec chronicles there are strong statements against those who would drink to excess, but the very fact that there are such strong condemnations of drunkenness suggest a social evil that was a continuing threat. Gideon planned to use that tendency to the Limhites’ advantage.
Gideon suggests taking not only the people, but the flocks and herds. That is a lot of extra baggage that might burden them. He is apparently counting on a good head start over the Lamanite pursuers. It is also an indication that they are intending to begin a life in a new area. They do not intend to arrive completely destitute in their new homes.