Mya Davies, 20, from Craven Arms, and her boyfriend Lewis Smith, 21, from Wem, set off on Friday to climb Ben Nevis in Scotland before attempting to conquer Scafell Peak in England on Saturday and Snowdon (Yr Wyddfa) in Wales on Sunday.
One thing they didn't expect was to suffer sunburn, and Mya said that on Monday at work her burnt skin was causing more problems than aching legs.
The couple have raised nearly £2,000 for the Severn Hospice, which cared for Lewis's dad, Stewart, before he died, and supported the family after his death.
Mya, a health care assistant at Ludlow Hospital, said: "We had so much support from so many people, some being anonymous so we would like to say thank you.
"Severn Hospice is an amazing charity. They helped Lewis's father and family at the end of his life when they were caring for him."
The couple planned all their accommodation in advance and have supported each other in the gym.
"It was really good," said Mya. "The hardest part was the climb up Scafell Pike, it's really steep."
Lewis, who works at Budgen Motors in Shrewsbury, had said that his dad had climbed Ben Nevis and Scafell but never managed to see Snowdon.
Nicky Green, community fundraiser at Severn Hospice said: "What Mya and Lewis did for us was outstanding. Their families must be so proud of them, just as we are - they took on the Three Peaks and they did it.
"When they called me from Ben Nevis to update me on how they were doing, I was so pleased to hear from them, and it shows what a kind and thoughtful couple they are.
"We are incredibly touched and can't thank them enough for their support."
The fundraising page is at justgiving.com/fundraising/Mya-Davis