It sounds like the two of you have really done a remarkable amount of groundwork! Great job.
It's really not possible to predict just when one of you will click with someone - so thinking about how you think you would feel depending on "who goes first" is fine but you won't REALLY know until you get there.
In terms of advice? No matter how slow you go it is very possible that one of you will have flashes of - doubts, jealousy, insecurity, whatever - that doesn't mean that you're doing it wrong, it means that you are trying something new and learning about yourself as you do.
(In my blog here I talk about my first jealousy moment and how it resolved - it's here if you want to read it:
We learned that for us the best answer was to ... pause. To not react to the negative reaction right away. To let it percolate a bit. So it might go something like this:
Something is said or done.
Someone has a negative reaction.
- pause - (thinking about it)
Other person is informed about the negative reaction.
- pause - (thinking about it withOUT responding right away)
First person is informed about Second persons response to that reaction.
- pause - (both people thinking about the other persons perspective)
THEN the conversation starts...
For us these pauses may be minutes or hours or overnight depending on how long it takes for each of us to get out from under the influence of our negative reaction and see things more objectively.
Wow, sorry this turned into more of a "How to fight with your spouse" essay then I intended. My point is, there will be bumps in the road, which you already know, if you and your spouse continue to communicate as well as it sounds like you have so far - I think that you have a great chance at building something wonderful!