Started as he got a restraining order on her with custody of the child.

I also wouldn't mess with a single mom's alimony, custody agreements, and general stability.  

To address your other question about pricing: there are full custodial IRA’s and there are checkbook IRA’s, aka IRA LLC.  

Here are some of the reasons why: Compared to an IRA, Solo 401k contribution limits are roughly ten times higher.There is no custodial requirement for the 401k.You don't need the additional expense and administration of an LLC to have checkbook control.There is a built in-Roth component whereas IRAs are either traditional or Roth, not both.A spouse can also participate in the same Solo 401k plan.The Solo 401k has additional tax benefits over an IRA when investing into real estate using leverage.The penalties for prohibited transactions are less severe, though it's best not to utilize this benefit :)

Another reason to use this method is there are never any delays in the deposits having to do with a third party, and only one institution (mine) has custody over the deposits.  

Open custodial account   2.

Whichever you do, make sure you have checkbook control so you can invest quicker and avoid custodial fees each time you invest.   

There are full custodial plans and checkbook plans as I mentioned and either of these can be set up with companies that act as plan document provider.   

The party with custody of the funds has the legal obligation to do this under the tax law if they hold the sales proceeds.

I had planned to open both custodial accounts and Roth IRA for them, then pay them through online payment from our business account to their custodial accounts, then transfer the money into their Roth IRA accounts.