having a problem with my control

So, I've been lucid dreaming for a while now, my guess is at a little less than 10 years. When I was young I found that simply shouting very loud, I'd wake up, so as a result I've never had what some would call a "nightmare". Which I was very glad about.

The last few years though, I've been able to bring people into my dreams. Sometimes, when I start in an area with a large crowd of people (a common setting for my dreams), I find someone that looks like an idealized version of me and tell them who I want to see. It always works, technically... the people do come, or at least something close to it (usually depends on how well I know the person). The problem? Well, one of two things almost always happens.

Either, A.) I get greedy, bring more people in than I'm "allowed" and they start turning into mutants... or B.) I see them coming to me, but before I can see them face to face, or interact with them everything starts to blur and then poof, it's gone.

It's been very rare that I can hold onto a dream that's doing that, the only thing I've found to work is to look around at other things and such.

Anyway, my question is this: Is there anyway you know of to hold onto these dreams? Why are they happening once I call for someone? Is it because of the excitement of seeing that person? If so, how can I remedy it all? Bottom line: I want to be able to bring people into my dreams, and keep them there, instead of being almost instantly thrown out the second they're about to come into a good view.

If this has happened a lot, it may be happening because you are now expecting it to happen. Before you sleep, try to plan what you are going to do when you meet the desired person(s) Write out a scenario if it helps and think it over as you fall asleep, this will help with your expectation, you know what is going to happen when you see the person, therfore you won't be expecting it to end. Try to stick to whatever plans you made for the dream, after a while you should be able to spontaniously decide to do different things but this should help for the time being.
Have you tried rubbing your hands or spinning around when you notice the dream fading? if not these are proven methods for prolonging LDs
Hope this helps, I've never had this problem so my reply is meerly a stab in the dark.
Good Luck!

The best tips have already been given by Ubik, but I just thought i'd add another one. Fasten your seatbelt, here it comes:

You could try to ask someone (for instance the person that's helping you bring the other people into your dream) how you can get them to come in withough anything going wrong They will surely be able to help. If not, try to persuade them, as you are dreaming and as such, there's no way it's impossible, or ask someone else. You might for instance call for a dreamguide, which would be the (dream)incarnation of your subconcious, and could help you with matters of dream control, or even remind to become lucid the next time you're dreaming (it's said that DCs will show up to appointments in other dreams :D ).