You should be congratulated for doing the right thing. It is neccessary for you to have your marriage blessed, it is the right, moral thing. That pretty much makes everyone’s ‘feelings’ on the subject null & void. My suspicions are that if they think your intentions are ‘materialistic’ they are somehow assuming you are requesting gifts. My suggestion would be to be very upfront about the reason behind your actions. That you are simply righting a wrong in the eyes of God and all you want from them is to come and witness the blessing of your union and I’d just CLEARLY indicate their PRESENCE is the best PRESENT you could recieve. Kind of hard to accuse you of being materialistic with that!
Best of luck and hope you are able to get it all done soon!