Both players have linked up with the Dons on their pre-season training camp in Ireland, where fellow trialist Deon Burton has also travelled with Karl Robinson's side.
Riordan, best known for his excellent goalscoring record at Hibs where he scored 54 times in 123 appearances, played for St Johnstone in the SPL last season after a short spell with Chinese Super League club Shaanxi Chan-Ba.
The 29-year-old played a handful of times for Scotland and was sold to Celtic in 2006, but he failed to make much of an impression in Glasgow and returned to Hibs in 2008, scoring a further 36 goals in just over 100 games before leaving on a free and moving to China last summer. After not being offered a deal by St Johnstone, Riordan has now been invited to join the Dons on their trip to Dublin.
Juanfri was last at Malaga. The 22-year-old was tipped for big things when he made his first-team debut aged 16 but only played a handful of times for the La Liga club.
Meanwhile, Robinson has revealed he is flying a centre-back over to Ireland this week for a medical ahead of a proposed move to stadiummk.