Wow, you could be me on the other end! My fiance actually just converted through the RCIA, even though all his family is Methodist, and under severe opposition from his stepfather! But from what I know, the Methodist church and the Catholic Church are really not so far off from their basic foundation. I’ve actually heard a Methodist or two describe themselves as “lazy Catholics”.

(They don’t go to church for a workout!!) Though my fiance’s immediate family no longer practices, his grandparents are extremely dedicated Methodists, and they were just thrilled that he’d found a place for God in his life again! They even sent him little cards for his confirmation. And actually, through sponsoring my fiance and attending RCIA, I even discovered a lot I hadn’t known before. For one thing, the Catholic faith is (one of the only) Christian faiths that believes you don’t necessarily have to be Catholic (insert denomination here) to go to heaven. The Church doesn’t teach that you won’t be saved unless you’re Catholic! Of course, there are other paths to salvation, we simply have the rare luxury of FULL understanding of Christ’s presence in the Eucharist, contemplation of the mysteries, meditation on the sacraments, etc. as well as being part of the apostolic faith established by Christ Himself.
Now, 5 years ago, when we first started dating and he found out I was Catholic, he made it painfully clear right out of the gate, that he had ended relationships in the past because the girl wanted him to convert to Catholicism. I told him he would receive no such pressure from me, but on the rare occasion that he would attend mass with me and my family, I think he really missed having God so close in his life, and that seeing us all sharing in communion with God’s love, he felt like he was really missing out. He made the decision about a year ago all on his own to start going to RCIA classes, and has since become an even better Catholic than me! (I know, you always hear that!!)
Many of the candidates in our RCIA class had been married to a Catholic for many years, and were just now deciding to become Catholic themselves, and I think that for some people, they just have to get over the “stigma” most Protestants can have about the Catholic faith. Really, I think your husband may feel a bit guilty about turning his back on his family, so to speak. I know my fiance had a few issues about that in the beginning, not so much from his mother, but his stepdad’s words were ringing in his ears…“What will your grandparents think when they hear this???” But his grandmother is the most loving and understanding person, and her excitement for him coming to God and a deeper understanding of his faith, I think really gave him a lot of confidence in his decision. I wonder if your husband has talked to any of his family members at all about this?
We’re not yet married, and have no children, so I can’t say I speak from experience, but I excitedly anticipate the day we can pack up the kids, and all attend mass as a family. And I must say, it may sound strange, but I am able to love him on such a deeper level, now that we can share in every facet of our lives. I never felt unfulfilled before, but I can’t imagine our relationship now, without our faith as a central core. Looking back, I think of how empty that must have felt. Really, I think you should pray for him, that God speaks to him, and he is able to reconnect with his faith in some way…Catholic or not! Hope this helps.
Best Wishes!!