In response to the original question, as others have said, in general mountain bikers are a pretty considerate bunch, especially when there are kids involved. There are some self-absorbed knobs, but thankfully they're pretty rare (they're in all probability self-absorbed knobs off the trails too).
Yes, keep your ears tuned to what's going on around you. If another rider is sitting behind you for a while, it's likely they're not riding much faster than you and will wait for a safe place to pass. Even more so if they know the trails and where the passing spots are. Still, call out, "want to pass?", then act according to their reply. Significantly faster riders will appear behind you pretty suddenly but will usually call "track please" or similar to let you know they're there. If there are several riders, the leader should tell you how many are in the group so you know to leave enough space. Let them know you've heard them, and you'll call them through when you feel it's safe. There isn't really a preference for left or right, it's dependent on the particular trail; when you've found a safe spot to pull aside just call out "go left" or "go right" so they know which side to pass you on. With a well-picked passing spot, you don't have to stop to let them through..If you stop for any reason, pull off the track, no exceptions. OK, unless you're really hurt and can't move. For anything else, move aside to keep the trail clear for others.
Riding around Red Hill there is a fair possibility of encountering horse riders on some of the roadside shared trails. Meeting head-on is usually OK, as the horses are less prone to be spooked because they'll see you. Pull aside & stop and let them past, or if the rider says it's OK, slowly keep riding until clear. Approaching from behind is more dicey, because the horse may hear you before you've seen it and get spooked. As soon as you see a horse,speak out to let both it and the rider know you're not a predator; horses are generally trained (to varying degrees depending on age) to recognise human voices so they'll be less likely to take fright. Wait until the rider calls you through before passing. However, sometimes you may encounter larger groups and in these instances it's better just to duck out to the road for a few hundred metres to get past them safely, then cut back into the trail.