Some thought, from an enterprise risk perspective, is needed before you move forward. In order to have confidence in (and therefore add some protection to your organizations brand) a "free from" type claim, you would need to consider:
- ingredients and formulation (you covered this, not intentionally adding gluten containing materials)
- supplier approval (risk of accidental, hidden, or contaminated raw materials coming into the facility)
- cross contact mitigation (you highlighted this as a risk - you use wheat flour in the facility)
- employee practices (are the aware of the need to protect the product)
Putting any verbiage on your consumer facing packaging indicating the product is made for those interested in gluten free products, you are targeting a higher risk consumer. My recommendation - if you are going to produce for a high risk group do it right, and have a full blown gluten management system im pace that mitigates your risks, otherwise you are likely to run into significant issues and do some damage to your brand.