Steve Staunton's team take on the Danes at the Parken Stadion in Aarhus on Wednesday evening.
But Sunderland centre-back McShane will not be involved after needing 10 stitches in a head injury sustained in Saturday's Premier League defeat at Wigan.
McShane was substituted after the aerial collision with Latics striker Antoine Sibierski.
The incident left the player needing treatment to his forehead following his second-half substitution, although his club hope he will be fit for the weekend clash against Liverpool.
Wolves striker Elliott was ruled out of Wolves' 3-1 win over Sheffield Wednesday by a foot injury picked up in training.
Darron Gibson was scheduled to assemble with the Republic of Ireland Under-21 squad on Monday ahead of Tuesday's friendly against Germany in Furth.
But the Manchester United midfielder has been drafted into the senior squad and will head out with the rest of the party to Copenhagen instead.
His place in the Under-21 squad goes to Bohemians winger John-Paul Kelly.