They were only told two weeks ago, after an MRI scan, that their precious three-year-old daughter was free of the brain tumour that had threatened her life for many weeks.
Their immense relief has made this holiday weekend all the sweeter.
However they remained concerned for Megan's health as she started the last intensive phase of her chemotherapy, which can be very tough physically.
"Megan received a three-hour blood transfusion and more of other drugs that help prevent her mouth breaking down as a result of the coming chemo," mum-of-four Sheila revealed.
"She was given Easter eggs by the staff and really enjoyed them. She might as well because everything will taste metallic from chemo."
Megan started her last batch of treatment on Thursday. She still has to undergo 27 hours of chemotherapy over the next week, then stem cell transplant after a two-day rest.
While the family had hoped to be back in Cill na Martra, Co Cork, in time for Megan to start school, it is now unlikely that she will be able to attend such a public place until next year.
However, the brave family could leave their provisional home, near New York's Presbyterian Hospital where Megan receives treatment, as early as this summer.
Dr Garvin who is treating Megan has advised that when her "treatment is complete she should remain in New York for a further three months because she will be immune-compromised and he does not advise flying home during that time".
"At the end of this period they will be doing another MRI," Sheila explained.
"One year after her treatment is complete, Megan will have to get all of her MMR shots repeated, because her immunity to these diseases will have been wiped clean by her treatment.
"But once she has received a flu shot he does not see any medical reason why she could not start playschool, assuming, of course, she no longer has cancer and assuming all of her class mates have had all of their shots."
Megan was diagnosed with spnet medullablastoma, a rare and aggressive type of cancer that attacked her brain and spine last October.
Doctors in Ireland estimated her chance of survival at just 10pc so the family of six moved to the Big Apple last December in the hope that Megan would receive specialist care that would increase the likelihood of recovery.
A massive fundraising drive helped pay for the move and an anonymous benefactor offered to pay for the little girl's medical costs.
Since their emigration, Megan has started walking and eating again.