Between September 2013 and April 2014, I led 26 storytimes. We took a few weeks off in November and December, otherwise every Friday morning I led two groups: 18-36 month old kids and 3-5 year old kids. We went through the alphabet, focusing on one topic a week that started with a specific letter (there were a couple of weeks that we doubled up in order to finish when we wanted to). The two groups had basically the same format, almost always using the same books, songs, and rhymes, but the younger group finished each session with a coloring page while the older group did a letter craft.
I enjoyed having a specific schedule to keep to, and the kids enjoyed guessing each week what the topic would be based on what letter we were on. My alphabet crafts were a huge hit, many families requested the supplies for weeks they missed, as they were hanging all of the crafts around their bedrooms and playrooms.
Next year I plan to simply use topics again, somewhat seasonally. If I can get into a three-year rotation of storytime plans, most kids will have something fresh every year they come.
What I'm unsure about is how to break the groups. I offered three storytime sessions this year -- 0-18 months, 18-36 months, and 3-5 years. My baby group had 2-3 kids off and on for a few months, then after Christmas no one came. My other two groups averaged 6-7 kids a week. A few kids in the older class had younger siblings who could have attended the younger class, but of course parents only wanted to come once. During summer, we offer one storytime for all kids 2-5 years, and it's sometimes difficult to find crafts that all ages can do.
Currently, during my break between regular-session storytime and summer, I'm offering a Music & Movement program (a post on that is coming!) for all ages. I've had 14-15 kids each week. But dancing to music is something any age can easily do...
Maybe I'll see how this summer goes, and plan to expand my regular-session storytime into one larger group as well. But there's no way those 15-18 month old walking kids could fit in with either the little babies nor the 4 year old preschoolers... Hmm...