Charles has missed the Dons’ last two matches – a draw against Peterborough and Tuesday’s 3-0 defeat to Blackburn – with a hip injury but could return at the weekend.
Will Nightingale is nearing a return after a lengthy spell out with a knee injury but this game could come too soon for him.
Striker Joe Pigott is available to return to the starting XI should Neal Ardley choose to make changes.
Charlton will be without Ahmed Kashi and Jay Dasilva after the pair suffered injuries in last weekend’s defeat to Shrewsbury.
Kashi will be out for at least four weeks after injuring his right foot in the closing stage of the 2-0 home loss.
Chelsea loanee Dasilva, meanwhile, was taken off after 72 minutes against the Shrews with an ankle problem and faces up to six weeks on the sidelines.
Goalkeeper Dillon Phillips is expected to return to the squad after recovering from concussion.
Watford boss Javi Gracia does not think Abdoulaye Doucoure's form will be affected by his omission from France's latest squad.