Another vote for Magic Dust. Be sure to grind the sugar, chile powder and pepper (if used) into dust, too. Be careful to avoid heating the sugar too much. I ‘grind’ in the blender and the friction from the spinning blade makes dry things get hot more quickly than you might expect.
I like various Cajun dry rubs on smoked ribs and grilled meats in general. A good commercial one is “Slap Ya Mama,” from Walker & Sons, Ville Platte, Louisiana. (Don’t show the can to your mother.). Cajun seasoning is spicy, but not hot.
At the other end of the country is “Famous Dave’s Rib Rub,” from Eden Prairie, Minnesota. I picked up a jar of this on a Chicago trip earlier this year and like it a lot. Contains dried lemon and orange peel, which isn’t common in a rib rub. This runs about as hot as you’d expect of a Minnesota dry rub.
My wife and I really like Head Country which is available from Amazon. I like spicy but Mrs. Glinley does not at all and she will eat anything I put it on. Their sauce is probably the most popular one here in Oklahoma since it’s a local product. It’s also sweet and not spicy.
Thanks for all these suggestions. I’m going to order both Famous Dave’s and Head Country. I’m a bit more wary of the Cajun offering, even though I agree that Cajun flavoring is often not “hot,” but it might be a bit too . . . assertive for her.
I’ll put in a recommendation for Penzey’s BBQ 3000 rub, which is smoky but not hot, IMO. I’ve used it successfully on baby backs in the past. I’ve found it to be particularly effective with a maple glaze.