I have to admit that I’m not entirely familiar with the blessing of weddings. Maybe one of the other folks on here can tackle that one. My knowledge of the Mormon church is limited to what I’ve heard from former members such as yourself, but from what I know, I understand your trepidation when it comes to joining another church. Pretty much all of us that have come to the faith from another tradition have struggled with the same feelings to one degree or another, albeit not to the extent that you are. I’m going to take a stab at your question here, but realize that the answer you get is going to depend completely on who answers. The Catholic Church teaches that all the various Christian denominations contain Truth in one form or another, but only the Catholic Church contains the fullness of truth. The Catholic Answers (not the forums) website contains a lot of tracts that cover arguements posed by people of various faiths, including the Mormons. They also explain some of the basic tenets of the faith. The Catholic faith traces its roots all the way back to when Jesus Christ himself founded it in 33 AD, so there’s a lot of information to sort through. I know well how overwhelming that can be. An online version of everything that the Church teaches can be found here.
Once you feel like you can handle it, I would recommend either calling a nearby parish and seeing if you can meet with the priest to discuss your situation or attending Mass and trying to talk to him afterwards. He will be able to give you more in depth information tailored to your specific needs.
God bless you, and know that you and your family will be in my prayers.
EDIT: I forgot to mention that if you do attend Mass, please be aware that Communion (also called the Eucharist) is closed, meaning that it is reserved for Church members only. Other than that, you are perfectly welcome to participate.