Byrnes has recently played as a central defender for Melbourne Victory in the Hyundai A-League. Sherman has been playing for Whittlesea Zebras, in the Victorian Premier League, also in Australia, and has represented Australia Schoolboys.
United will play Sam Oji, a 22 year old centre-back, who was with Leyton Orient last season, has previously been on Arsenal and Birmingham City's books, and made 13 senior appearances last season.
Northern Ireland U18 left back Brewster Frizzell and Frank Belt, a right-back, both of whom have been released by Hull City, could also appear.
Frizzell was called up to the Northern Ireland U19's European Championship squad, while Belt spent time last season on loan at Bridlington.
The left-back Michael Lea, the former Manchester United player, who has been on trial for just under two weeks, will also play.
Check back on Iron-Bru.net later tonight for a match report and photos.