While Mads is normally spot on, I wonder if this time he’s misunderstood, and you want to use material that’s been offered for free, if you can find it?
I’d have a different concern, however. Ifyour sons are many, many miles away and not involved with you in the production of your planned videos for their music, might it be better to leave it all in their capable hands? They can take responsibility for finding music video practitioners who can help them develop the video look and feel they want to best represent their music to their market. Time to let go, perhaps …?