Centre of Excellence player Halford will compete for Scotland in the International Youth Toto Cup in Austria between the 21st and 29th August 2007.
Halford leaves to join up with the squad consisting of players from teams such as Glasgow Rangers, Manchester City, Motherwell and Heart of Midlothian on August 21.
Paul Driver, head of youth at Nene Park, said: "This is a great opportunity for Lewis to progress further with the Scottish squad.
"There are some bright prospects within the group that he is going out with to Austria and he has a confidence in his own ability. That means being around them will only help his game."
Meanwhile, fellow Centre of Excellence player McDonald will represent Wales in the Pembroke Cup when his country hosts the Republic of Ireland at the end of August.
Wales will be hoping to avenge that defeat in the Pembroke Cup, an important part of their preparation for the Victory Shield, a tournament between Wales, England, Scotland and Northern Ireland televised live on Sky Sports which gives young players an opportunity to showcase their talent live on television.
Driver added: "Aynsley has had a very encouraging pre-season playing in all of the youth team games and securing a starting place in the line-up for the first Puma Youth Alliance game against Northampton Town, so he is in good stead to impress in the upcoming matches for his country.
"His involvement over the past year with the Welsh squad has also clearly helped with his development as he pushes to gain a place in their Victory Shield team."
Like a number of Diamonds players, Halford and McDonald started their time with the club training and playing for the Elite Centre squad before making the successful progression through to the full Centre of Excellence programme.
Source: http://www.confguide.com/newsArticle.do?id=6948