I understand your dilemma shannon, as i was a landlord some year's back. The first thing to remember is that tenent's have more right's than the landlord, i know...ugh! The first thing you need to do is to contact the Landlord's Association and see what YOUR rright's are. There is a noise ordinace in every County and Town, see what your's is. Here it's 11 p.m.
You can send him a certified letter telling him of all your concern's, but do it professionally as tenent's will scream discrimination and lack of privacy. His argument will be that he pay's his rent so he is entitled to live in peace and harmony in his dwelling. The loud and annoying sex would certainly make me mad. Some people are more vocal that other's, but it's up to them to keep it to a dull roar. With you having children, that is where my gripe would be. Outline your concern's to him and end it by asking him to please comply with your request's so you all can live in a safe and comfortable environment. Let him know that if thing's don't calm down a bit you will have no choice but to take it to the next level. Let him know that you are not pissed as he may take it as a threat.
Landlord's have to be real careful and select their word's accordingly. Tenent's have a ton of right's. Even tho it's your responsibility and your in charge, they are protected under tenant's right's law's. Did you contact the owner of the property? Let them be the bad guy's. I see that you are the manager but who is the physical owner?