Stringing beads isn't as easy as it looks. It takes two hands, and each one has to do something different than the other one. Then, if it is a fat string and a small hole, it requires shifting repetitively with the thumb and index finger. So many of the little children I work with can't string beads whether it be due to stiff fingers, weak muscle strength, low vision, or a poor attention span. That is why I am always looking for toys that are adapted or easier for a special needs child to succeed. A few years ago while I was at an OT home visit, I fell in love with the lace up pup toy that the little boy had in his toy box. It has large holes which makes it easy to stick the lace through. It also has a wooden "needle" at the end to help the string go in the hole better, as well as tucking it back through the end when you are finished with the activity...no more lost beads! Here is a link that has a picture and purchase info:
Amazon.com: IQ Preschool Lace up Pup: Toys & Games
I own the pup, but it also comes in a snake. My two year old son loves to play with it. When he lets me sneak it away from home, I take it on home visits to use with some of my clients. "Testing" toys out allows the parents to decide if they want to go buy it or not...I always hate to suggest buying a toy unless the child has tried it out first. Lately, I have seen children with diagnoses of cerebral palsy, down syndrome, and autism be successful with this toy whereas they weren't with other stringing bead sets. I'm not making any money off of suggesting this link, it just happens to be one of my favorite toys in my "OT bag".