"I didn't want to do anything until I knew my daughter was going to be able to walk down that aisle as a flower girl," Still says.

By Nicole Weisensee Egan
Updated April 20, 2016 01:15 PM
Credit: Gillian Laub

After nearly two years together, most of it long distance, NFL defensive tackle Devon Still knew Asha Joyce was the woman he wanted to spend the rest of his life with – he just hadn’t proposed yet.

Then he found out his then four-year-old daughter, Leah, had stage 4 neuroblastoma, a rare and deadly childhood cancer that had spread throughout her body.

A few weeks later – on July 11, 2014 – he popped the question.

“I proposed to her at that particular because I kinda knew I wasn’t going to be there mentally for her because of what my daughter was going through,” Devon, who recently signed with the Houston Texans, tells PEOPLE, “so I felt as though proposing to her let her know that no matter what I wasn’t going to leave her side.”

They both understood the actual wedding would have to wait until Leah was healthy again, he says.

“Planning your wedding is supposed to be a happy event and there was no possible way we were going to be able to be happy throughout that time with my daughter going through it and the uncertainty if she was going to make it through.

“So my plan was to put it on hold after we got engaged and just focus on Leah and nurse her back to health so she could be our flower girl,” he says.

Devon mostly kept their engagement quiet, focusing on Leah’s fight to survive on his Instagram account – until he and Leah were honored with the Jimmy V Perseverance Award at ESPN’s ESPYs last July – after Leah was declared cancer free.

“There were weeks where we would go out and not show any type of affection – no no hugs, no kisses – because I was so mentally drained from everything I was going through,” he said in his emotional speech. “And you stood by my side.

“You didn t have the typical engagement where you sit down and you plan everything because I didn’t want to do anything until I knew my daughter was going to be able to walk down that aisle as a flower girl,” Still said, his voice shaking. “And I thank you for being so unselfish and I promise you I’m going to try to give you the wedding of your dreams.”

Representatives from The Knot heard his emotional speech – and offered to foot the bill for that dream wedding he’d promised her, picking up the tab for everything from the invitations to the wedding dress to the honeymoon.

America has been voting on each detail of the day since March 16 and will continue to do so through May 4. The wedding is May 13. So far the invitations, the flowers, cake, wedding gown and bridesmaid dresses have been chosen.

And yes, Leah is the flower girl. She’s even designing her own dress.

The Knot added an extra detail just for them: Instead of gifts, the couple created a registry to raise money for four different cancer charities (including the one Devon started) – a cause that is near and dear to their hearts.

While Leah is healthy now, her doctors still only give her a 50/50 chance of survival long term so going for her follow-up tests to see if the cancer has returned is rough, he admits.

“Parents of children with cancer call it scan-xiety,” he says. “You know your child’s in remission but when you have to go get those scans to see if they’re still in remission it’s nerve wracking because you don’t want to hear those words again – that your child has cancer after everything you’ve been through. But so far so good.”

To follow Devon, Asha and Leah’s journey to their dream day, be sure to follow the hashtag #theknotdreamwedding and to donate to the Still Strong Foundation, The V Foundation for Cancer Research, St. Jude Children’s Research Hospital or the Alfred I. duPont Hospital for Children, through their charity registry, powered by Crowdrise.

For more on Devon, Leah and Asha’s story pick up this week’s PEOPLE, on newsstands Friday.