YG, just wanted to write to offer my sympathies with your situation.
My mum was widowed when I was 6 - I was an only child.
My dad's family had arranged for him to be buried with his mum and dad because he married so late in life they did'nt want him to be on his own - so the grave was already paid for.
However my mum had all the funeral expenses including having his body moved over 70 miles from the hospital he died in to his grave, which was about 90 miles from where we lived, but virtually on thier doorstep. My unlce lent my mum the money for his own brothers funeral but saw she paid it back at £5 a month (all she could afford) which took her well over a decade.
And we only ever got to see his grave once or twice a year and normally combined it with a visit to his family. My mum did what she felt was the "right thing" by trying to keep in touch with her in-laws for my sake. But as I got older and realised she was struggling to do this, as like you she did all the leg work, I actually got really cross with them for the way she was treated.
What I have read about you puts me in mind of this situation all over again. Be strong for your girls and be dignified, I know from another of your posts you are a very caring person and I am sure your girls will realise as they grow just how much heartache their dads family has caused you at a time when you should all be pulling together.
25 years after my dad's death I could walk past any of his family in street and not recognise them. I only get and send Christmas card with one of them, and all her news talks about people I am related to but I could'nt tell you how for all the tea in China