Edwards, who helped guide Wales to Saturday's RBS 6 Nations Championship defeat of England and ,of course, the Championship crown, flew out to Grenoble to assist head coach Lewis and his assistants Shaun Connor and Ioan Cunningham.
Victory against the Scots would send Wales into the top four against the winners of the England v Georgia game.
Lewis said: "Everyone is looking forward to the game and to have Shaun out here to help with our preparation is obviously a major boost. He arrived with a smile on his face, of course, and his input will no doubt further develop our players' defensive work.
"Our philosophy is to challenge the opposition with the ball in hand whenever possible and although everyone wants a win, we won't forgo that philosophy. We have got a younger group of players than the group that played against England and France in recent weeks. But there is a great spirit within the camp and the game can't come soon enough for the players."
Wales Under 18 FIRA-AER squad: Keagan Bale (Dragons), Robert Lewis (Blues), Ryan Elias (Scarlets), Torin Myhill (Scarlets), Dillon Lewis (Blues), Alex Jeffries (Dragons), Gareth Allen (Dragons), Rory Thornton (Ospreys), Adam Williams (Ospreys), Michael Snook (Blues), Oliver Griffiths (Dragons), Tom Phillips (Scarlets), Jonathon Fox (Ospreys), Tom Williams (Blues), Matthew Marley (Blues), Daniel Brooks (Ospreys), Ben Calder (Exiles), Luke Price (Ospreys), Daniel Jones (Scarlets), Joe Thomas (Ospreys),Tyler Morgan (Dragons), Garyn Smith (Blues) Dafydd Howells (Ospreys), Rhys Williams (Exiles), Josh Adams (Scarlets), James Whittingham (Blues)