But to choose to have sex and avoid having children is missing out in blessings that God has in store for you.
I know the point you are making, but I just think that has a lot more to do with personal preferences for wanting to raise kids than it does with scripture. We have many choices in life these days and there is nothing wrong with making those choices that are not condemned as sin nor will result in condemnation.
I like kids and have nothing against them nor against all who enjoy raising them even though I was in a situation where raising my own wasn't wise or practical for me. I suppose that puts me in a place where from my point of view I think we need to recognize our own personal preferences or even the specific will of God just for us, and not impose that on others by trying to make them feel guilty or saying they are out of the will of God just because they don't have the same calling or preferences we do. I mean, I COULD take Pauls comments on staying single out of context and use them to say everyone who gets married is out of Gods will and missing out on His blessings, but I don't. I realize that is not what Paul was saying when I read his comments in the context they were written.
I just really haven't seen anything in scripture saying it is Gods will or command that every person has to raise children or they will miss out on something good for them (something that can't be replaced with some other blessing instead). Of course things like vasectomies or birth control pills weren't mentioned because they didn't exist when scripture was written, but there were other ways of avoiding pregnancy (not just abstinence) that were practiced even back in Jesus time and I don't see any condemnation in scripture that is read and understood within the context it was written.
Sure, kids are a blessing for those who want to raise them and are in a position to do so (married, etc.) But there are many things that are blessings from God that not everyone takes advantage of or that may not be a blessing to every person. Lacking any scripture for us today, especially in light of Paul's comments on marriage and family life, I don't believe there is any command to have kids nor do I see any threat or warning about a person who chooses not to have kids missing out on a blessed life. I also just don't see any condemnation on enjoying sex while avoiding pregnancy. That seems like a personal preference to me. God has many ways to bless us in many different circumstances and lifestyles.