Brazil international Jesus, who made an instant impact after joining City in January with three goals in four league games, returned to training earlier this month after suffering a foot injury against Bournemouth in February.
"He's much, much better. Today he made part of the training with us," Guardiola told a news conference on Friday.
"He's coming back with his happiness and we are so happy he is back again.
"All the squad are going to travel as a group to Wembley so he will be part of that. After that we are going to see."
The Spanish manager ruled out defender John Stones for the weekend's clash because of a muscular problem.
A visit to Wembley has a special significance for Guardiola, who picked up two European Cups with Barcelona at the venue - one as a player and one as a manager.
He won 21 trophies in seven years while in charge of Barcelona and Bayern Munich.
"Wembley is important part of my life," Guardiola said. "I would like to win the FA Cup to prove to my players in their heads how good they are.
"You realise you have lived that experience and when you win a title or a final it is a lot of stress and pressure. When you handle that and are able to win, the next time will be a little bit easier."
City have won the FA Cup five times, with the last victory coming against Stoke City in 2011 under Italian manager Roberto Mancini. (Reporting by Hardik Vyas in Bengaluru; editing by Andrew Roche)