I just planned several of them (3 of them) right after my wedding last year.
Going with a theme does make it a bit easier sometimes. You could use anything from baby bottles, diapers or a gender theme.
Sometimes finding the perfect invitation is a great starting point and you can work with decoration ideas from there.
You can buy premade invites from your local discount store (here we have Target and Walmart) or your local craft store. You can also have them printed (I found a place online to do them).
I really think the invites are the starting point. I think it sets the tone for the shower, including food, decorations and games.
Games, well it really depends on you since your the host. Games I included for the showers I planned were
Name that song- Have each guest name as many songs they can that include "baby" in the title. This should be timed. You can vary this and have them include the artist as well if you would like to make it more difficult.
Examples-
Baby Got Back - Sir Mix A Lot
Hit Me Baby- Britany Spears
You get the idea.
Baby Bingo- You can find printable sheets online of Bingo Cards. While the guest of honor (mom to be) opens gifts, the guests will cover the bingo spot with the corresponding gift. The cards have common baby items, bottles, diapers, blankets listed. You can have them use a writing utensil to mark out each item as it is opened. Whoever has bingo first gets the prize.
Dirty Diaper game- You can buy a newborn pack of diapers (we actually picked some up from the restrooms in baby stores here and there, lol) and you melt different candy bars in each one and mark them with a letter for your master sheet.
We did 5 candy bars total for the five diapers. Twix, Mr. Goodbar, snickers, KitKat, Reeses. You wouldn't believe how closely melted candy bars resemble baby poo. Put one bar in each diaper, melted it in the microwave and closed the diaper up. Marked it with A B C D E for the master sheet. They are then passed around and the guests have to guess what candy bar is in each one on a sheet of paper.
Whoever has the most correct wins.
I will include some links at the end here for decorating ideas and more games.
Registry info is OK to be included with the shower invitations. It is the purpose of the shower, to shower the mom to be with gifts. Totally fine to do that.
Food- well it is up to do. We usually have showers mid afternoon around here about 2. We have apps and finger foods. Mini croissant sandwiches, fruit and veggie tray, dips with various breads, chicken roll ups. Variety of foods and also a small dessert. We also always have a bakery cake with well wishes on it for the mom to be. I made a Tiramisu cake from allrecipes.com for my youngest sisters shower in Nov. because she loves tiramisu.
For favors- they aren't really necessary. Only the last shower I hosted did we give out favors. I think this is actually a newer trend for baby showers opposed to weddings, they have always had favors.
For the last shower I did, I bought MiniBons from Cinnabon, Don't know if you have them in your area though. I put a minibon in a cello wrapper with a tag on it that said, "Thanks from (insert Mom to be's name here) Bun in the oven.
I did find some really cute candles online with this same saying but I liked the edible part better.
It is okay to do a meal but I personally prefer finger foods. A meal is something you generally have to keep warm until serving so it it usually more difficult to do. It is completely up to you. Showers can become very costly depending on how much you want to do.
Keep that in mind when deciding.
FOr the game gifts we bought many inexpenisve but very useful things.
A cosmetic bag with First Aid items in it. Band Aids, neosporin, alcohol swabs....
Candy dish filled with the candy bars we had for the diaper game winner.
Stationary set
I-tunes gift card for the winner of the music game.
Here are some links for you
I used this site a lot.
http://www.babyshower101.com/
http://www.peekaboopumpkin.com/pages/baby-shower-invitations.php?gclid=CN2f2NTGgpkCFQsMGgod8G6ykg
http://www.tinyprints.com/baby-shower-invitations.htm
http://www.polkadotdesign.com/catalog/Baby_Child/Baby_Shower_Invitations?gclid=CLnelePGgpkCFQu-GgodNxQNoA
These last three sites I really liked for invites.
Since I already know you like allrecipes, they have a great section for appetizers if you choose to go that route.
The first link has pretty much everything for baby showers.
ETA- even if this wasn't planned or joyous for her to be preggo, she will have a different feeling when she has the baby. A baby is a huge miracle and I can only imagine she will feel differently when she has it. I am sure everything will work out for her. Life creates it's own path, we choose which way to go. Send her my well wishes and let me know if/when she finds out what she is having. I would like to send something your way for her!