I've spent so much time focusing on piano lessons, that I've neglected to address my early childhood music classes until now! It's a downright shame, too, because teaching my little ones is one of my favorite parts of teaching! Thanks, Joy, for posting about your early childhood class ideas and reminding me to get on it! I'm borrowing your list of things to consider as a jumping off point. (Hope you don't mind!)
The larger the space, the better... sometimes! I've learned that having too much space can be distracting to children, and they spend more time running around then participating! If you're looking for a place to teach, I would search out area dance studios. Their rooms are usually the perfect size and many studios (at least in my area) are willing to rent out space in the mornings when they aren't offering classes- anything to defray the cost of rent, especially in this economy!
The class I teach is Mommy & Me, due to the fact that it's during a morning out program at a local church. However, even if it wasn't, I wouldn't teach these little ones without their Mommies around! It's great for these little ones to see their Moms enjoying the music, and it gives them the chance to make awesome memories together.
You'll need a wide selection of music and child friendly musical instruments. I keep Egg Shaker Pairs, Castanets, Sandblocks, Rhythm Sticks and Scarves handy - enough for each child to have one or two (see class size below). I also have some ribbon dancers that I made (I'll post about those before too long).
I also use a wide variety of music. I love Rachel Rambach's songs, as well as music from Baby Einstein (Particularly the "Meet The Orchestra" CD) and Wee Sing. I used to feel tremendously guilty about using Baby Einstein and Wee Sing, but the kids LOVE it. (Another word of advice, don't feel guilty about using the same songs over and over, particularly if the kids like the songs. Preschoolers LOVE repetition.)
Generally, I limit all of my classes to 6-10 students. For the early childhood classes, I try to keep it at 6-8. Too many small children = lots of chaos!
With this age range, 30 minutes is about all I can get before the kids begin to lose interest. Kindermusik offers 45 minute classes for this age range. I think it really depends on your group of kids, and what type of activities you incorporate. I believe Kindermusik may also include a story and craft project (although I can't swear by it) which might help to hold interest a little bit longer!
I recommend charging monthly for early childhood classes, but I would also give parents the opportunity to pay for an 8 week (two month) session and only charge the for 7 weeks, making it clear that this is the better option. (So that if you have to miss a week, you're not losing money - it's not uncommon with early childhood classes for things to come up unexpectedly, and I like to be flexible!)
At this age, my main goal is for the children to enjoy and LOVE music. However, I also use it to introduce students to basic aural skills (high/low, fast/slow, etc.)
Hope that these thoughts help! Please let me know if you have any specific questions, and I'll do my best to answer them!