Winger Buckley this week arrived from League Two leaders Rochdale from an undisclosed fee while midfielder McGinn, the recent signing from St Mirren, was an unused substitute during Saturday's defeat at Blackpool.
Scott Severin remains the only injury doubt with a groin problem.
Fellow midfielder Jon Harley will be involved despite an enquiry from Bristol City this week.
Teenage defender Rob Kiernan has linked up with Scottish Premier League side Kilmarnock for a trial.
The visit of Swansea is Watford's first home game of 2010 and they are without a win since beating QPR at the start of December.
Recent signing Shefki Kuqi could make his first start for Swansea.
The Finland striker was on the bench for the midweek stalemate against Coventry after signing on a free transfer from German Second Division side TuS Koblenz earlier this week.
A lack of goals has been the Swans' Achilles heel this season and boss Paulo Sousa is hoping Kuqi will make a difference, with the much-travelled 33-year-old set to replace Gorka Pintado in the starting line-up.
Sousa must decide whether to recall Leon Britton to the squad after omitting the diminutive midfielder against the Sky Blues amid speculation he is set to leave the club.
Playmaker Andrea Orlandi came through the game against Chris Coleman's side after recovering from a thigh injury and is expected to keep his place, but a doubt remains over Cedric van der Gun (hamstring).
Joe Allen will be hoping to get the nod over Jordi Lopez in midfield but defender Albert Serran (hamstring) remains on the sidelines.
Sporting Life