The father of a guy in our minyan is not Shomer Mizwot and his father (i.e. the original guy's paternal grandfather) passed away. I asked my Rav if the guy in our minyan can recite Qaddish in memory of his paternal grandfather in place of his father - may he live and be well.
My Rav replied:
- He must request permission from his father (whose father passed away)
- He should recite Qaddish `Al Yisra'el year-round
- He should recite Qaddish Yehe Shelama during the week in which his paternal grandfather passed away
- He should hold a Se`udat Azkarah (memorial meal) in honor of his paternal grandfather on the day he passed away
Based on my Rav's ruling, I would suggest:
- Explicitly granting your son permission to recite Qaddish in honor of your mother
- Having your son recite all of the Qaddishim which you would have recited yourself
In other words, all other things equal (including the assumption that your son will be able to properly recite Qaddish), there is no need to delegate the Qaddish to anyone other than your son - may you all live and be well.
As always, CYLOR.