Questions about changing orders

[Crockpot]

I've previously posted that my SO's ex does not have a car (SO is NCP, dad).  CP/BM won't be getting one anytime soon.  Because she can't meet at the designated exchange point between our houses, SO has to drive much further to see kids.  It's very likely his Wed night visits will end because by the time he gets to their house he'll have to return them less than an hour later and we can't afford for him to eat out with them every week (and the gas!).  They were coming to our house for a family dinner.

His current Wed. time is 5pm-7pm on school nights and until 8pm on non-school nights.  This order was signed in March when BM had a car.  We'd like to extend our Wed visits to overnights so SO can see them.  We can get them to school in the AM when necessary.  Is her lack of transportation enough change in circumstance to get this changed?  More often than not, they've stayed overnight on Wed this summer to accommodate SO's need to get them to summer school (because BM has no transportation).  So we have a pattern of this already happening.  BM will not agree to it unless it's court ordered.  

Another question.  To add a first refusal clause to an order do you need to justify it being added?  I ask because BM lost her daycare recently.  She brought the kids to her sister's house for the week.  She's basically made it impossible for SO to see kids this week since they are so far away.  She didn't ask SO if either of us (or his mom) could watch them.  The kids spend so much time away from their mom it's ridiculous.  We don't have a lot documented on this, thus the question about justifying the order.

Thanks.