I agree with Rocky_Girl.
If you dont believe in JW doctrines anymore and only attend for family, why do you feel the need to partake at thier memorial? Are you really rejecting Jesus if you dont partake from them?
The bread and wine are prayed over by JW's at their version of a service commemorating Jesus' death. If you no longer agree with them, why participate in thier service any more than you have to?
Since your attending for family, how will they view you if you partake? Maybe observe somewhere else?