I'm a bit excited about the prospect!
But on the other hand -- do I want to marry outside the faith? How likely is it that somewhere in the group I will meet someone and we fall in love but are different faiths? I went through that once, being married to a Christian Scientist (NOT Scientology) and our hearts never could fully share the same love of God and life because his understanding was so limited and false (CS believes Jesus was just a 'good guy' not God, don't believe in sin or hell, believe that as long as they are not caught doing something then they are not guilty of it, fine with birth control, etc) and I really would love to share fully with a husband rather than have such a dichotomy again.
Would you join a non-Catholic but Christian group? Will it be more like searching on Match or other dating sites where the quality of matches is less likely to result in a good and Godly match, or would you have high hopes?
There's really no Protestant denomination that won't cause you and your family a problem. You won't be able to share in their bread & wine ceremonies and he won't be able to participate in the Eucharist. That will be perceived as a not-so-subtle "snub". And your heart will be a little less full.
The key foundational belief of Protestantism is that Catholicism MUST be wrong (otherwise there is no reason for Protestantism to exist). Will he understand that you need to take your children to Catholic mass and that they shouldn't go to his non-denom (or Lutheran or Episcopalian or whatever) Church? And both your hearts are torn a bit more.
You also have a responsibility to the young'uns under your roof. You want to set them on the path to heaven of course. Imagine the impact on them if your new Protestant husband starts explaining why birth control is okay. Or why Protestantism is better for him than Catholicism. Or makes an inadvertent negative comment on some news story about Catholicism. Or he wants to sleep in on Sunday. Or any of a hundred points of difference in his faith. Your kids need to be deepening their faith to prepare themselves for the onslaught that secular society has waiting for them. Mixed messages at home will only breed indifferentism in them, a belief that such credos are interchangeable, and ultimately unimportant. And your heart will break even more.
Protestant moral systems are typically more humanistic, and tend towards the "anything goes" end of the spectrum. The sacraments, sin, female priests, homosexuality, birth control, even abortion may be up for debate. Will you be able and willing to correct such false impressions in your children? Or will you stay quiet, in a futile attempt to foster marital harmony?
And what lessons will you kids learn knowing that you are dating Protestants? That their Catholic faith isn't that important, after all?
Finally, there is the possibility of misrepresentation. Dating is commonly part of the marriage discernment process. But if you're not there to discern marriage, will your date be told that upfront? "Yes, I'll accept your invitation to dinner and a movie, but I could never marry you." Be sure your video recorder is running. His reaction will be priceless.
In terms of broadening your "reach", joining such a Christian singles group would seem to be a positive at first glance, but the chances of a positive outcome are very slim indeed.
And I say this as as someone who once walked down that road.
"I should not believe the Gospel except on the authority of the Catholic Church."
-- Augustine of Hippo
Dating is emotional. It makes me feel somewhat vulnerable. I wouldn't want to bring temptation into that mix.
Jack has pointed out that Protestantism has no reason to exist if Catholicism is true. Take it from a former Protestant. He's right! Jack also brings out some excellent points. Which faith will you pass on to the children? If everything is the same and it doesn't matter. But it does matter! Wasn't it JPII who called the family the "domestic church". We are held accountable for what we pass on to our kids. Even someone like myself who doesn't have kids of my own it's still incumbent upon me to pass on a sense of reverence and respect for the Mass and the things of God. I showing my little niece how to cross herself. She's 2 and a half and she almost gets it. Her parents show her too. But I help out too. I'm passing the Faith on to the next generation. Wish that were taken more seriously here.
As Kathy has pointed out, marriage is about sharing everything, both the good and the bad. You're not going to share your Catholic Faith with him or her? I don't think so!!!
Someone else posted Protestants are going to Heaven. Not the point. The Church doesn't recommend we marry outside the Faith. I'll stick with the Church's recommendations, that you.
THE SYLLABUS OF ERRORS CONDEMNED BY PIUS IX
III. INDIFFERENTISM, LATITUDINARIANISM
15. Every man is free to embrace and profess that religion which, guided by the light of reason, he shall consider true. -- Allocution "Maxima quidem," June 9, 1862; Damnatio "Multiplices inter," June 10, 1851.
16. Man may, in the observance of any religion whatever, find the way of eternal salvation, and arrive at eternal salvation. -- Encyclical "Qui pluribus," Nov. 9, 1846.
17. Good hope at least is to be entertained of the eternal salvation of all those who are not at all in the true Church of Christ. -- Encyclical "Quanto conficiamur," Aug. 10, 1863, etc.
18. Protestantism is nothing more than another form of the same true Christian religion, in which form it is given to please God equally as in the Catholic Church. -- Encyclical "Noscitis," Dec. 8, 1849.