I'm sorry for your loss. You should deal with it however you feel is best, and if that's avoiding weddings then so be it. Just be aware though that if your wife deals with things drastically differently this may cause issues. A friend of mine lost her only son at 17 five years ago, and almost split with her husband because they dealt with things so, so differently.
Over time, you might change your mind. Things are raw for you now, and the way you feel now won't be the same as you feel in 1, 2, 5, or 10 years. That's not me saying you'll get over it, but you will see different situations in different ways, and you may feel that you want to attend weddings to those close to you.
My friend who lost her son felt exactly the same. We used to have a memorial gathering for him every year, but this year she stopped it because she said it was too painful seeing his friends coming having reached an age he would never reach, driving a car, with girlfriends, some with kids .. it's just like rubbing it in.
But now, she has started to go to things like weddings and parties again. She is getting counselling for her grief and, though difficult, she says it does help her.
You are not being unreasonable for not wanting to go to weddings right now, however you shouldn't make a statement that you will NEVER go, as you should always allow yourself the space to assess how you feel and change your mind in the future if appropriate :).