Four thoughts. First, define what maximum and minimum effort estimate is acceptable - for example, tasks should not take less than 2 hours or more than 4. Second, communicate that contingency shouldn't be included in the estimates so they aren't padded. Instead, have some room in the overall plan...
Have you had any meetings with buyers for retail distribution? Projection is difficult because the success of the product honestly depends on your external ability to market and more importantly, how accessible the retailer allows your product to be at the store level.