Send out STDs as soon as you have a date/time/place squared away to give people as much time as possible to plan and save... I made my wedding website right away and sent out an email save the date right away then sent out a real save the date about a year out, maybe less I can't quite remember. Some people send out newletters to update people will lots of info between the STD and invite. I sent out my invites about 3 months ahead of time and already had an idea of who was and wasn't coming (a few surprises were thrown in here but not too many), and I just sent out a newletter with info about the day and the cruise 1 month out.
As for OOT bags, they aren't just for cruise brides, people make them for their normal weddings for people who come from far away to welcome them to the area so I think they are a great option to help welcome guests but are completely optional, you should feel like you have to do them if it is getting too confusing figuring out who to give them too. When I started I guessed that around 50 people would come to the wedding and started buying things that I could find later if I needed them (ie tissues and puzzles), and then once I had a final count I bought the actual bags and more specific things. And I was right about my guestimation, I have 44 coming so it worked out well. Hope this helps!