Like Tambling, Brown was likely to win a place at the Olympics even if she did not compete in Budapest.
The teenager, who won park bronze at Tokyo 2020, suffered a medial collateral ligament (MCL) tear in April and had to perform in a supportive brace.
Her dad Stewart told BBC Sport they had argued about her competing, but as the event wore on it became clear that her final position would affect whether best friend Sakura Yosozumi could qualify from Japan.
Brown finished second in the women’s park event to ensure Yosozumi would join her in Paris.
“We kind of argued about three weeks ago, [I said] ‘Sky, let your knee heal’. But she really wanted to come and she promised me she’d skate kind of safely,” Stewart Brown told BBC Sport.
“Then Sakura got knocked out and we realised if we didn’t help keep the rest of the girls down a bit that she wouldn’t qualify for the Olympics. She woke up this morning and said let’s just do this for Sakura.”
Sky Brown added: “For Sakura to make it to Paris, I had to finish in the top two and everything I just did was all for her. I had nothing to lose and I wanted to skate for Sakura.
“I didn’t use all my tricks and I’m saving some for Paris too which is definitely a confidence boost.
“I’m so excited to eat chocolate croissants.”
Macdonald, meanwhile, will turn 51 five days after the Paris Olympics begin on 26 July and says he thought he needed a “miracle” to qualify.
He is an X Games record-holder, is good friends with Tony Hawk and has skated through the White House, but Paris will mark his Olympic debut.
Born in Massachusetts, he qualifies to compete for Great Britain through his Luton-born father.
“I’m going to Paris, it’s pretty surreal, it’s amazing – such a happy moment,” he told BBC Sport.
“A combination of luck and the stars and planets aligning. I’m 50 years old and going to the Olympics as a skateboarder. Who would have thought it?”