I think am going to run an old school style D&D game for them. Right now leaning towards using books that I already own (Moldvay B/X and Tim Brannan's The Witch). I'll start them at the Keep on the Borderlands and mix in some OSR adventures that I have (possibly even Death Frost Doom).
However, the release of Eldritch Witchery has me looking at Spellcraft & Swordplay.
Either way there's going to be old school goodness and witches.