I really can empathize with you! Over the past few months, I've noticed that those I help so much, and go out of my way for, are the ones that take me for granted. Sometimes, I think it's because they feel they can walk all over us, as they think we are "too nice".
It's a terrible predicament. Sometimes, I sit here, and wonder why everything gets handed down to me, because "she'll sort it out", but then I thought maybe it's because they know we are willing too, and so presume that to be the case 24/7.
It's hard, because you wonder whether you should try and make more friends, which can be hard..but then you resent that too, because you think why should you have to? You were there for them, can't it be mutual?
I think the best thing, is to be happy you have two that are coming, and however hard, don't let it ruin your fun. If there is anything you feel you can be doing to liven them up, then try it...but sometimes it's just best to flipping let them get on with it! & to learn the hard way.