Here is an assortment of ideas that your kids will enjoy:
Custom Stationary
A fun idea for your child, which may also end up being a great gift for your child, is custom stationary. Give your child plain paper and pens and markers in colors that will reproduce well (yellow is not the best color, especially on white paper). The trick is to decorate the header, footer, and margin areas of the page, leaving the center area blank for writing.
Have your child make several different sheets of custom stationary in different styles. Ask him or her to choose a favorite from them. Later, take that sheet to a print shop, and have stationary with matching envelopes printed as a gift for your child. If you have a desktop publishing program, you may be able to scan and print the items yourself. Your child will love sending letters to grandparents or pen pals with his or her very own custom designed stationary set.
Family Newsletter
If your child likes to write and enjoys using the computer, he or she can design a family newsletter. Your child can add funny stories, special events, photos, and birthday or anniversary wishes for extended family members to read and enjoy.
You can copy the newsletter on a copy machine, have copies printed at a print shop, print copies from your computer, or create an email newsletter, so your little editor can show his or her stuff.
Today in History
You and your child can do a little research online and collect interesting historical facts for a given date. Any day is fine, but doing this on special occasions and sharing with others is also a charming idea. Send Grandpa a list of neat things that occurred on his birthday, or create a chart for the date a new baby was born into the family, or mark any event using this idea.