The Light Ball-Volt Tackle mechanic works so that either parent can hold it and if the resultant offspring is a Pichu, then it will have Volt Tackle.
So given that offspring Pokemon inherit the mother's species and the father's compatible moves, breeding a female Pikachu/Raichu and a male Luxray with Charge should result in a Pichu with Volt Tackle and Charge. Of course, the male Pokemon can be any Pokemon that can learn Charge and is in the Ground or Fairy egg groups. These criteria are satisfied by Luxray, but could also be satisfied by Luxray's evolutions, Mareep and evolutions, Electrike and evolution, Plusle and Minun.
Hope I helped. :)