Your fear about disrupting the work environment is unfound, because the work environment is already disrupted by these incidents. Your job now is to prevent further disruptions by ensuring that such incidents won't repeat. 

I do not know which cultural circle you are from. But if you were in my cultural circle (central European) then I would recommend this course of action:

1. Decide for yourself, perhaps in consultation with the owner, what disciplinary measures you are going to take now and what measures you are willing to enact if the behavior continues.
2. Plan a private meeting with the employee accused of harassment
3. Tell them what they are accused of
4. Let the employee explain his behavior
5. Wait until he is finished
6. Tell him the consequences his behavior has now and what consequences there will be if the behavior continues
7. Inform the people who complained that you have taken care of the situation and that they should report to you immediately if they again become victims of inappropriate behavior.