Your feelings are very personal and you need to work them out with your wife. About all I can tell you after 47 years of marriage is the things we do together seem to be enriched by many other things that we do independently. Perhaps you can come to some accommodation where you take turns with the baby sitting.
I cannot speak to your dance environment, perhaps it is more sexually charged than mine. My wife and I take lessons together and dance together at parties. However, we both dance with other partners regularly. We also take lessons separately. I often take group lessons and partner several ladies. I also have a competitive partner with whom I dance frequently and my wife is in complete agreement. An onlooker might perceive our body contact in standard dances as sexual but it is absolutely functional. In latin dance, where there are many sexual undertones, it is theatrical rather than romantic.
You say "I would rather her not go without me" but I am left wondering if you expect to be able to go out without her. Take a good look at yourself and make sure the real issue is not loss of control.