Both children were also excluded from various sports and play because of their 'conditions'.
The mother, from Croydon, south London, who cannot be named for legal reasons "lied at every opportunity" by telling medics her children suffered from autism, asthma, urology and gastric conditions.
She was jailed when she appeared at Croydon Crown Court for sentencing.
Andrew Evans, prosecuting, said: "So serious the degree of financial loss... makes this case one of the largest benefits overpayments attributable to a single claimant which the Department for Work and Pensions has recorded."
Judge Elizabeth Smaller said she subjected her son to a "serious and irreversible" operation.
The mother also claimed she was a single parent when she lived in a succession of houses with the children's father.
Judge Smaller said: "Most people seek nothing but pleasure from their children and most people wish their children most of all good health.
"That was the starting point for the many doctors and medical professionals to whom you made your false and hugely exaggerated representations and they believed you because why would a parent present their children as ill if they were not?
"They believed you because you were extremely plausible in your presentation, often anxious and tearful in their clinics.
"I'm satisfied that you sought every opportunity to present your children... as suffering with a variety of conditions."
The judge also said the scam could have been stopped if specialists had not ignored the opinion of a GP who became concerned over the situation.
Judge Smaller said: "Dr Hart sounded an alarm bell about this mother in May 2010 writing to those doctors to whom these children had been referred in the most esteemed teaching hospitals in this capital, only to find herself inadequately supported, and as she says - rebuffed.
"Eminent though those doctors are and at the forefront of medicine in their respective fields - with only one exception, what none of them did was pick up the phone and speak to Dr Hart.
"Dr Hart - viewing herself as merely a humble general paediatrician who deferred to those specialists - felt unsupported in 2010 and unable to bring about any intervention in this family.
"It is a matter of regret that such qualified and experienced medical professionals at world renowned hospitals did not maintain better channels of communication."
The children, who are now being fostered, both had various risky operations under general anaesthetic.
The trial was shown evidence that the children were eating normally on trips to McDonald's and Toby Carvery.
Judge Smaller added: "I'm of the view that your continued representational fraud was with the intention of obtaining the highest possible levels of discomfiture benefits.
"I'm also of the view that the sympathy and attention you got for being a struggling mother of such ill children was also a very considerable draw for your offending."
She jailed her for all 15 counts for seven-and-a-half years to run concurrently.
