"Wayy too soon to be thinking about love!!" I hear you.
I read through your thread again, and sorted two main strands: How long it took to get to kissing in the first place; and how to improve the quality of the kiss itself.
What shines through to me from all you write here, is that you care enough about him to consult, think and plan, and you and your ex have got a continuity of caring shown by being able to discuss your shared past frankly enough that it may serve as a resource for your future with the new guy [Much respect to the both of you]. Also, that while you have been patient with the new guy's 'slowness', and he has not tried to rush you, you want to be on his mind while you are away, and maybe for him to be there when you get back.
I'll look at the strands:
Regarding how long it took in the first place: I want to say that I reckon this 'chaperoned' sleepover will be very, very special to him, as it will be to you, regardless of whether more or less than high or medium quality kissing takes place: if neither of you goes further nor less far than you would if you were not going away, I believe it is already a special enough event to signal that you intend reunion on your return!
Regarding the quality of the kiss: I reckon you need to build a bridge between his kissing and yours - if you're interested, here's one way how: While you're reviewing in detail, in your mind's body, all the kissing so far - like you did earlier in the thread - then just for a while, go ahead and 'step into his shoes', and in your mind's body 'be' the one kissing like that. Grok him - become his moves and rhythms. Then step 'back into your own body', 'be' on the recieving end, and feel what you would need to do to synchronize with that kind of kiss?
Put that aside for a moment as you go back and remember some of your very favorite kissing, your best kissing of all time, both as receiver and also as giver - in your mind's body, in his shoes/mouth and back your own shoes/mouth. Now relive those extra-special times when the 'giving' and 'recieving' blended into sharing - both 'directions' occuring simultaneously.
Now fantasise morphing - gradually shifting between these. Be thorough, for it is through these you may teach him the art of kissing conversation. Take your time, and enjoy the process as you sometimes start with his present way of kissing, sometimes your own, sometimes leading, sometimes being led. If a transition feels a bit jolty or jarring, then that's OK because you are by yourself! And you can ponder and think through what needs to happen to make it less jolty and more smooth. Sometimes stroking, for example, his cheek slowly, might give him the 'pace' you want - gentle and firm, to get through beyond whatever thoughts/feelings might be flitting through his mind. It's a non-verbal equivalent of Poetry's 'easy now, tiger', a friendly, perhaps even reassuring 'slow down' message.
Anyway, the above is a recipe: doing it comfortably can take less than a minute, unless you like to take things slowly and enjoy practicing even more. Though it is right to WAKE UP as from a reverie and put this to the back of your mind - especially when you are with him. If you drive a car, you will recall how smooth and natural driving processes used to be 'bit by bit' until integrated. Let's face it, you were pleasantly surprised by that more recent kiss, and it is very likely things may get even better without explicitly remembering all the above, though if you read through and 'walk through' a few times thinking of him, then WAKE UP, this may soon only take a split-second, and especially at those most appropriate half-seconds as they gradually lengthen until you either need to breathe, or share circular and nose-breathing until you both fall asleep on the couch, and your friend quietly turns off the DVD and puts a blanket over the two of you.
Speaking of which, is the sleepover set up yet? And how long are you going to be away? I'm still rooting for it to be everything you could wish it to be, both at the time and as you think back to it
Best wishes