The conversation has to be embedded into the curriculum or you risk othering people, which is the exact opposite of you want. That would mean a variety of dolls, stories, and lessons that speak of the value of inclusiveness on the a daily basis, also look at your staff? Are the administrators and or teachers one race or gender and the assistants all another, if it is, whatever you do in regards to workshop isn't going to do much as your culture is stating you support oppression.
It is a long process.
A good reference are starting off point is Louise Derman-Sparks and this book:
Anti-Bias Education for Young Children and Ourselves
In my experience, it's great for adults to get comfortable talking about our racial identities with one another first. Sometimes we "try things out" with children before we ever take the time and courage to work with these questions together with other adults. Once we are comfortable talking about race with one another, it comes more naturally with children, and we are less likely to "other" children and families.kp