2000Greetings is a great place to start. They provide free greeting cards, and other e-cards for all types of situations be they romantic, funny, or for love.
Hallmark has a lot of different things, I am sure they would have large birthday cards. I have seen these at Wal-Mart as well. I do not know about American Greeting Cards, though.
A great website is http://www.egreetings.com/, where they have a wide selection of greeting cards. They have many cards for different occasions including birthday cards, sympathy cards, and even cards that welcome people home which would be great for your situation.
I would recommend to try going to Greeting Card Universe. They stock all different types of birthday ecards and greeting cards, even those for a 107th birthday.
There are many retail stores that carry "Happy Birthday" greeting cards. Some examples of these stores would be Hallmark, Target, Walmart, and Toys'R'Us.
A great option would be to send free online greeting cards. A good website for this would be http://www.123greetings.com/. They have a wide variety of online greeting cards for a number of occasions!
Stores to buy nice birthday/greeting cards would come from places like Target, Wall-Mart ,Dollar tree. As long as it fits your taste you can find a card.
Giftah has an excellent selection of cards from the Happy Holidays brand of greeting cards. Another place to try would be Hallmark Greeting cards stores.
Riverside cards offers a consignment service, check out their website.
One of the best places to get a card would have to be Hallmark because their business is revolved around cards. Also the reason you should get a card from their is because they have some really funny ones for birthday parties and if you want, they even have music ones.
It depends on how much and how many you would like to have,
Send thank you cards, thanking the sender for thinking of you, and make sure you send them a card on their birthday. A verbal thank you will do. Only the Greeting card industry and the postal service would want you to send a thank you card for a Birthday Greeting, the recipient who, in turn would feel obligated to return a thank you for the thank you card to which you would have to respond in kind....a never ending cycle of joy for Hallmark I would imagine..
Since Jehovah's Witnesses do not celebrate birthdays, you would use the same greeting that you do any other day of the week.