Your XW is really not doing any work on herself right now. Distracting via work, travel, OM are all examples of this, as is her limited time with her kids.
I'd strongly consider a strong legal play at this time. A court-order revisiting child visitation/custody/support that holds her to her responsibilities as a mother. You may be doing too much as a single parent - let her do more.
All is fair in love and war - and her being ordered to be a more involved mother (or paying the financial price of higher child support, and more structured visitation) will be a bigger pill to swallow for any OM. IMHO this is rougher for OM than for OW, as who wants to help raise some other guy's kids. Men are hard-wired to resent this. Importantly, it also will be a great way to remind her of you - as each child as a nice dose of you in them - and they are a constant reminder of your M.
If you do the above, do so in a matter-of-fact, objective manner, knowing that it'll help your children in the longrun, protecting yourself from holding any retaliatory/revengeful motives against her, and keeping low expectations.
