When do you send the invitations?  

I would say no later than the first of November. it may sound early, but you want to make sure you give people plenty of notice so other plans are not made.

First off, huge congratulations to the mommy to be. I've seen baby shower invitations sent out in all sorts of ways. I've had some that came a month before the shower to the most recent one that we've been invited to came two weeks before the shower.
When the proper time to send them out is, I'm not sure, but for me I prefer to get them about 2-3 weeks before the shower because that way I'm not really likely to have plans, but I also am not as likely to forget about the baby shower.

I would make sure to send them out at least a month in advance - so therefore first of November is the best time. This gives people enough time to buy gifts and figure out whether or not they'll be able to get off work. I'd try to get people to RSVP at least 1 week if not 2 weeks beforehand therefore at that point you can really worry about food etc. that you'll need to be buying. But make sure you go to stores and make the baby wish lists etc. and send that along with the invitations.

About a month in advance is always a good idea. it gives the person you're inviting a chance to make sure that they're not going to be doing anything that day, and so they won't make any other plans. But it's not to far in advance that they forget about it. That's happened to me before. If you send it to early, it won't be near the front of their minds, and they may forget about it on the day it comes.

Invites really depend on what they're for! If it's something really important that you want people to know about way ahead of time so they can "mark their calendars" I would say about a month and a 1/2 ahead. That way they have about a month before they need to RSVP. I would say send them out no later than a month before. Sounds like the case for your party.

If it's something like a child's birthday party I'd say about 3-4 weeks before hand would be good!

You should probably send them out a month in advance, if not sooner. That way in gives those that are invited a chance to prepare for it like buy a present, make arrangements at work, and any other arrangements that may be needed to be made. It also gives you a better chance at securing the date so that others won't have plans already made for the same day.

I hope this helps!

Happy mylotting!