"Send money to Mr. Weasley, explain that it was entirely his fault that the wand was broken ... ask him to buy Ron a new wand."
About taking the blame:
Ron's wand = Ron's responsibility.
Arthur Weasley seems a very fair man who wont agree to put the blame on Harry for something the boys did together. Even if he wouldn't connect the flying car prank with the broken wand,
he'd ask Ron what exactly happened. Then, Ron would freak out (doubly). First, because Harry went behind his back and second, the money issue.
Though in the film he acts more calmly, in the book Arthur Weasley got into a brawl with Lucius Malfoy when he was mocked for being too poor to equip his kids for school. (CoS, CH4) I am not sure it would be such a good idea to send money to him implying he cant afford replacement wand. In GoF Harry gives money to the twins to help them to open a shop and for Ron's dressrobes.
I doubt very much Harry, who'd just that summer had met Ron's parents would dare to give money to Molly or Arthur. They're not that familiar, it'd be too awkward for everyone concerned, not to mention very insulting to the Weasleys.
To give money to the twins in CoS for Ron isn't an option either, they were younger, how would they explain where they'd got it? To Percy - again, too awkward.
Also after the boys stealing the car and causing humiliation (and a ministry inquiry) to Mr. Weasley, maybe it's not the wisest action to draw attention to the broken wand. Chances are Ron havent told them it got trashed. Or maybe they knew but Molly decided it'd be a good lesson for Ron to struggle with a faulty wand, so next time he'd think twice before pulling something reckless.
"Send the money to Weasley's anonymously"
No way. Arthur Weasley is a ministry employee, if he knows what's good for him he won't accept a knut from an unknown source.
"Heck, he could have just sent it through the teachers ( McGonagall) as well, so Weasley's would have less hesitation to refuse."
That's the worst option. It's like asking Minerva McGonagall to send charity to the Weasleys. "Here, dear parents, we in Howarts have a special fund for orohans and the poor who are struggling to buy school supplies for their kids. Take this donation and please buy Ron a wand." That's just...
Either way, if Ron would find out he'd flip his lid. Like in GoF, when he realised the galleons he paid back Harry with were false.
I think the best option would be indeed to ask help from the head of Gryff, McGonagall. But without involving the Weasleys. To give her money and ask her to buy a (temporary) wand for Ron, asking her to pretend she had a replacement wand in her posession saying:
"As it happens, I have a spare wand that belonged to my great-aunt Beulah. I am lending it to you till your wand is replaced, Mr Weasley, so you wont cause chaos and destruction in my Transfiguration classroom."
And then when his parents will see it fit and have the money they'll buy him a new wand that choses him or whatever.
But yes, the plot device of the broken wand (just to have it fire back the 'oblivate' at Lockhart) was esespecially lame. It makes the teachers who allow Ron to use a faulty wand irresponsible and negligent, especially since they themselves (Snape and Minerva) remark on how dangerous it is.