The estimated likes per day can greatly vary as reported. One marketing I had on a local city initially reports only 2 ~ 9 likes per day but on actual it yields to 27 for the first 8 hours of the campaign. So just launch the campaign and observe.
There are many factors the affects the yield of your campaign, make sure it is visually appealing, interesting, suggests something to do and always know your clients first to yield better results.