"Is it possible to really love someone and sleep with another?"
Sure. People do it all the time. Is it advisable? Is it healthy? Is it something you'll regret?
You seem to want your cake and eat it too. My guess is that this indicates that you're actually more dissatisfied with your marriage than you're admitting to us. It seems to me that you wouldn't want to reconnect with your "friend" unless you weren't getting something you really need in your marriage.
If you are dissatisfied with your husband sexually, don't you think you owe it to him and your children to talk with him about it? You ought to be looking at what is driving you into the arms of another man, particularly if you still love your husband as you claim.
There are questions that you should ask yourself
There are also basic questions you should consider about yourself. What is missing from your life in general? A woman with three kids has her hands full. A woman your age is going to have questions about what adult life means. What kinds of things do you see yourself doing in 5 years, 10 years, 20 years? Your relationships are one facet of your life.
If you mess around with your marriage you escalate the drama and trauma of that relationship. If you're bored, I bet you could find something more creative to do with your time than fool around with old flames ... unless you like getting burned.