After you determine which model will work best for you, it's time to determine how many volunteers in each role you need.
Finding the right balance can be tricky. You don't want to leave students and instructors unsupported, but you want to have enough work for each volunteer that they feel like their time is valued and worthwhile. You definitely want to start out with both academics and experienced Wikipedia editors in your volunteer pool, however. Academics will be able to navigate the work inside the educational institution that needs to be done prior to the start of a Wikipedia assignment. And experienced Wikipedia editors can help head off problems that academics might not see. One common problem is that instructors usually encourage students to draw conclusions from the research they've done, writing "thesis statements" in many cases. Such original thought has no place in an encyclopedia, however. When Wikipedia editors work closely with instructors, they're able to create assignment plans that both meet the instructors' learning objectives and add quality content to Wikipedia.
Generally, good ratios when you begin is one trained Wikipedia Ambassador for every 10-15 students, and it's useful for students to have multiple points of contact, in case an Ambassador gets busy with other activities and can't support students anymore.