"We recommend initials..." An early version of the new DNA Confirmation page did recommend using initials. Subsequently, the use of initials was removed from the confirmation statements; see the example for Ancestry DNA. If initials are allowed (and I wish they were), it would be nice to know.
Only one tester needs to have a Wikitree account. If the other DNA match is a Wikitreer, you can confirm by DNA. See http://www.wikitree.com/wiki/Help:DNA_Confirmation.
The other option would be to convince your cousins to sign up for a family member account (you can create the account and invite them), add their DNA test, assign you as a profile manager, and then they can unsubscribe from emails. See Help:Suspending Your Participation. I know...I know. Easier said than done.