Beiju 88 birthday specific customs?

My mother-in-law will be 88 years old soon. We are going to Japan and we would like to have a traditional Beiju celebration. She has spoken of wearing a red kimono, walking in a parade holding a rice cake. Does anyone know all the little speific customs and procedures, so we can make this a truly special day for her?

When celebrating beiju in traditional style, the birthday person wears a cap (zukin) and a vest (chanchanko) and sits on a cushion (zabuton) all the color of gold and given from the family. Red is worn at "kanreki" which is the 60th (or 61st depending on the custom) birthday. From a quick search on the internet, rental costumes seem to be available. Of course, you can buy them, too. Here is a photograph of the costume.
http://shikitari.yuinoo.com/cyouzyu/index.htm

Since the costume is so embarassing for the modern elderlies, many people today prefer not to wear them. Then families might send modern clothing of that color, such as a yellow scarf of a more practical and sophisticated design.

I had never heard of parading, but the link above tells me that in the Edo era (17C - 19C), the birthday person used to go around the neighborhood delivering rice cakes (mochi) in which they wrote the letter "kotobuki" meaning celebration. Nowadays, people might just have a special birthday party with all the family together.

I suppose department stores are a good place to start asking for advise on what to prepare and what you can buy. If you have a Japanese department store near you, they may be able to help you. If not, you can try asking once you've arrived to Japan.

Customs differ greatly depending on the region, so when asking for further advise, it might help if you knew what part of Japan your mother-in-law is from or where her family roots are.

My mother-in-law grew up in the Ashikaga, Tochigi region. What is the cushion (zabuton) for?
Do we just have a special seat for her and place the cushion on the seat? Are there special foods that are served at a Beiju birthday? Pardon my ignorance, but do you serve birthday cake? Any help is welcomed.

Zabuton is what anyone puts underneath themselves when sitting Japanese style on the floor. It's just that in this particular occasion it should be the color of gold.

Birthdays, actually, weren't commonly celebrated in Japan in the pre-WW2 days. On New Year's day, everyone became an year older and they all just ate the New Year's feast.

Beiju and other elderlies' celebrations like Kanreki is said to have been celebrated on a "sekku" date which is January 1st, February 2nd, March 3rd, April 4th and so on, if you know what I mean.

Nowadays, everyone gets an year old on their birth date, and beiju is usually celebrated on the person's birth date as well. Having a Western style birthday cake is really up to the person or family. In general, traditional celebration feasts consists of things like "sekihan" (sticky rice cooked with azuki beans) and "tai no okashira-tsuki" (grilled sea bream with head and tail). You can order them in advance at any department store or decent hotel.

I'm not familiar about specific customs of Ashikaga. I hope someone else can answer that.