All four players were absent from the 1-0 defeat at Brentford on the final day of the Premier League season last Sunday due to unspecified injury and fitness issues.
Both Grealish and Dias have missed the last three games since City clinched their third successive Premier League title, while De Bruyne and Akanji have only featured for 69 and 57 minutes respectively across the same set of fixtures.
Man City have experienced a hectic fixture schedule in recent months as a result of chasing down a historic treble, with two huge finals up next against Man United and Inter Milan, facing the latter in the Champions League showpiece event on June 10.
Guardiola, who has understandably made widespread changes to his starting lineup over the last two weeks, is now hopeful that he will have the vast majority of his first-team squad available for Saturday's FA Cup final.
Man City players were given two days off following the defeat at Brentford before returning to training on Wednesday, with De Bruyne, Grealish, Dias and Akanji having all taken part in group sessions ahead of the trip to Wembley.
Specifically speaking at a press conference on Friday about the fitness of the Citizens quartet who missed out last weekend, Guardiola said: "They trained well last two sessions. They are all of them more or less fine."
De Bruyne and Grealish have been two of City's most influential players in attack this season and have contributed with five assists between them in this year's FA Cup; only Wrexham's Sam Dalby (four) has registered more assists than Grealish (three).
Meanwhile, Dias and Akanji have established themselves as two reliable defenders in Guardiola's unique system, with the former starting regularly in the centre of a back three and the latter showcasing his versatility by occupying positions across the backline, most recently on the left side in the absence of Nathan Ake.
Ake has since returned to full fitness after missing five games with a hamstring injury and played for just over an hour in the loss at Brentford last weekend.
Guardiola has also confirmed that goalkeeper Stefan Ortega will start between the sticks at the expense of first-choice shot-stopper Ederson.
"Yeah [Ortega] is going to play," said Guardiola. "I have always been like that in the FA Cup. At Barcelona and Bayern Munich as well. The keeper who plays in the FA Cup is going to play."
Ortega has kept five clean sheets in as many matches en route to the final, with City beating Chelsea, Arsenal, Bristol City, Burnley and Sheffield United to set up a showdown with Man United at Wembley.
Meanwhile, Red Devils boss Erik ten Hag has confirmed that Brazilian attacker Antony is unlikely to feature on Saturday after failing to make progress in his recovery from an ankle injury.