TIA,
It sounds to me that you have an opportunity to take another step towards BDSM and don't want to screw it up. That doesn't make you unsuited, to me it shows that you are loving and caring towards your wife and if you both continue in this direction, you will do so safely and carefully.
You have recognised that roleplay and fantasy are very different to reality, and to try some of your extremes on this first time would probably scare her from agreeing to do this again. I assume your objective is to have her enjoy the experience and want to do this more. As a Dom, I have always erred to the slower side, probably even slower than the subbie would have liked, but that does in turn build a trust and security that allowed things to progress over time. You have a lifetime together, take your time, you don't need to experience it all on day 1. It is fun to explore slowly together and get an understanding of your own feelings as they develop.
My suggestion would be that the night before the big day, you remind her of her commitment and give her a safeword that she may use if she is too uncomfortable with any task, or even just wants to come out of role so that she can discuss aspects with you. Apart from this time, she is be a obeydient, devoted slave to you.
The start of the day should have the basic 'rules' stated (the following aren't even suggestions, but more just examples) :
1. Slave (call her 'slave' or some other name than usual to reinforce her role) will obey all commands without question.
2. Slave will be naked or dressed only as I request for the duration.
3. Slave may not request or beg for anything for her own pleasure.
etc
Since you have only roleplayed in the bedroom previously, it is unlikely that she will be able to get thru the day without making several mistakes. Mistakes should be punished, but something mild will do for this first day. Say, a couple of swats on her butt with a wooden spoon.
Apart from servicing you whenever required (and of course, no pleasure for herself), the day does not need to be filled with wild BDSM adventures. The role (mindset) can be used for all the usual activities, such as cooking you breakfast, basic housework, etc.
It is difficult to give real suggestions to you, because of lack of knowledge of your tastes and experiences, but I would recommend you consider the following:
1. Public activity, remember that while she may be fully consensual to something in this area, the public she is exposed to did not give their consent.
2. Involving others, may be something you want to do another day if this is your kink, but on the first day you need to develop your own confidence of being in control. Without this confidence, you could easily lose control of events involving others.
3. Do not be afraid that you are being too mild for her. If you are too mild, she will let you know in your discussion with her after the day, and happily submit to another day - whereas, if you go too far, she will be hesitant to try it again.
4. As a vast generalisation, men tend to be aroused most by physical, women aroused more by the mind. What she physically has to do as a slave is far less important to her than the mindset that you create. So, washing the dishes after breakfast hardly sounds part of a wild kinky day, but if she is a slave cleaning up for her Master, it can be to her.
OK, I think I have rambled on long enough with my thoughts. Please feel free to ask for clarification on anything I have suggested.
I hope you have a wonderful day and it results in being just the first of many.
Brosco