I highly recommend practicing important speeches at Toastmasters.
Last year, I gave two important speeches in my personal life. One was a toast for a friend's wedding and the other was a speech at my father's 80th birthday party. I practiced by giving both speeches at Toastmasters.
I must say that it is very difficult delivering these kinds of speeches at a Toastmasters meeting - the environment is not the same as the event, the members of the club are unfamiliar with the topic of the speech. But practicing both these speeches at Toastmasters helped transform them from mediocre speeches to very good speeches and this was the direct result of feedback from the club and the experience of practicing them there.
Typically, at Toastmasters, we have one evaluator per speech. Because these were 'special' speeches, I asked that we did shorter evaluations by several members. This meant that three or four members would just stand up and give me their thoughts after my speech for about 30 seconds to 1 minute.
The feedback from the club was invaluable. I re-wrote both speeches to a large degree based on their input. I also practiced my pauses and worked on my overall delivery. A very kind senior member of my club also took the time to go over every sentence of each speech with me the next day one the phone. This gave me the confidence to know I had a good speech.
When I first delivered the speeches at Toastmasters, I would have rated those speeches both a 6 out of 10. When I delivered them at the wedding and at the birthday party, I would have rated those speeches close to 9 out of 10. There is no way I would have elevated those speeches to that level without the help of Toastmasters.
Practice your important speeches at Toastmasters, it will make your speech stronger and it will make you more confident when delivering on the big day.