Meaning you are ordering invitations from them or are you signed up there for receiving RSVP's? If you are ordering; just list the weddingwire website on the invite.
If you are doing everything online (not sure how minted works); then perhaps there is a link you could set up on your weddingwire website or a link on your weddingwire website you could link to minted?
WW is easier to use as your information here will go straight to your guests once responded. Become a premium member and the website is there at your fingertips available. This way you just put the site and your names for your guests to RSVP.