Well sub is who you are, so there really shouldn't be much change

A healthy way to transition from vanilla to D/s dynamic is that each person is just a little more open and a little more honest about their thoughts and desires than they were before.
1) you do not need to stop being the planner. If it makes you happy, makes him happy and you are good at it, there is no reason to stop! It is no less submissive of you or less Dominate of him for you to do planning. If it makes either of you unhappy, then worry about stepping up to the plate for change. Someone (or both of you) will have to put in some extra work to make the change successful.
One way to make this change could be seeking approval before and during the planning stage. It could help you feel more submissive and help him feel more involved.
2) Signalling playtime. This is really just the question "how do you seduce your man?" As a sub, seduction is probably our best artform. Most of us don't want to be direct or up front with our desires (although that is obviously the easiest rout and is a completely valid way of "signalling"). Everyone is going to be different here, but the question is, what do you want and what creative ways can you signal and entice him into doing what you want. It's like, if a brat wants some attention and spanking, sometimes they act out in playful sexy ways. "Acting out" in a way that you know gets you attention, but doing it while wearing something sexy, with the spanking toys conveniently located on the table of the next room may be an extremely strong signal, but you probably never needed to say a word haha.
Don't be discouraged if several of your first attempts at this don't work. Everyone is different and will respond to different signals in different ways. You just need to find out what works best for him.
If you have any more questions about a D/s dynamic or about the art of seduction, please don't hesitate to ask me ^.^ i know a great deal and have a lot of experience haha this reply was already boardering on tldr though :p