this is one of those situations where you have to return the karma,,, wish for three things the grand parents could use "together" like 2 new lawn chairs, 1 new bird feeder or really nice porch mobile, coffee mug set, wrist watches, you see where I'm going with this right?
if its something that's to be wrapped then when you unwrap it you act totally surprised and happy about "which one" they picked to buy and then you turn around and go this is really for you both to enjoy...
that will be special especially if all of you can do this together secretly.