Can my partners in my LLC keep me from coming to work because two employees who are their friends threaten to quit if I come back to the office?

What does the llc's operating agreement provide?  Assuming you have none (it can be oral), or that it is silent on the issue, members of an llc have no inherent right to be employed by it.  Moreover,  again unless the operating agreement provides otherwise, a vote of 2/.3 of the llc's equal members would be sufficient to fire an employee.  However, while you may have no right to work for the llc, you have a right, as a member, to all of the llc's financial information, and, in general terms, to be treated the same as other llc members with regard to distributions - if your son and daughter-in-law work for the llc, they are entitled to reasonable employment compensation and you, who no longer work for the llc, are not; however, you are entitled to comparable membership contributions.  You can sue to get the information, for your share of any distributions paid the other members, and possibly, if the other members have overreached, to dissolve and liquidate the llc.