Depends on the terms of the plan and the terms of the QDRO. Might be questions that you should direct to the Employer/plan sponsor.
By the way, have you sent the DRO to the plan sponsor? Only the plan sponsor can review a DRO to determine if it is "qualified", which is when it becomes a QDRO.
I'm of little help in utter disasters such as this (my instinct is "run away") but it might be helpful, or at least interesting, to know how this money got into their Schedule Cs - I assume the partnership cut checks and issued 1099s instead of K-1s? Did they still get K-1s?
It implies that someone knew that they "could" set up individual SEPs if they had Sch C income and did it deliberately. Just sayin'...
Should have said "no thanks" to this one. Lost money first year in on two plan years worth of "excitement". I reckon the SIMPLE IRA issue is on them and they can VCP if they choose to. Only 1 participant (family member) actually contributed to both. Regarding the late sign up of participants, either QNEC or throw your hands up to an auditor if they don't want to fund it. Think I will have an adult beverage(s) this weekend.
Here's Vanguard's sample IPS: https://institutional.vanguard.com/iam/pdf/IAMIPS.pdf
It may not match your needs, but it gives an example of things to include in your IPS.
You can see other samples by googling: investment policy statement template