Kane missed Wednesday's 2-1 win against Southampton with an ankle injury suffered against Everton on Friday and is in a race to make the Wembley showpiece against Manchester City.
Mason says Kane will be doing all he can to be fit for the final.
"With Harry it is just about taking it each day as it comes," Mason said. "We know he is doing absolutely everything he can to be back out on the football pitch.
For Southampton, they lost their 12th Premier League game from the last 15, meaning they are still not fully out of relegation danger.
They have experience of bouncing back from setbacks in recent years and striker Che Adams is expecting them to do it again.
"We need to show everyone what we're capable of and how we started the season so well," he told the club's official website.
"We did it last year when we went through a rocky spell but we came out on the brighter side so it's about doing that and staying together, because no one else is going to help us."