How much time do I have to send out thank you's before my guests start talking about me behind my back?

I want to do photo thank you cards but won't have pics for at least another 2 -3 weeks. Is 6 weeks too long?
I also really want to do an announcement card to send to the neighbors back home and a few of my parent's friends. Should I just let this one go? The pics my friends have forwarded are cute, but i think the photographer's shots will be better for this project.
Thoughts?