I'm speaking as somebody who has only gone through Hypnobirthing. I've heard of Hypnobabies but have not taken the class or tried it.
-Does anyone know an average of how much the classes are to take?
As PPs have said, it's hard to give an average, but in my mid-sized city in Idaho it costs $175-200 (ETA--for a 12-hour class).
As a homebirther, will the classes be geared towards me enough?
It will depend on the instructor. You might want to ask her about her experience working with home birth clients. My instructor was extremely pro-midwifery and worked with us well, (we used a freestanding birthing center), even though everyone else in the class was planning a hospital birth. She defended out-of-hospital birth quite diplomatically to her critics and just emphasized that the hospital birthers go in as informed consumers.
Be aware that other times, the course is offered in hospitals and is taught from a perspective that serves the interests of the hospital. Screen carefully!
- Can I successfully have a hypnobirth if I just use the CD's and read the book, but don't take the classes?
If you're a good and well-motivated independent learner, than you absolutely can.
In retrospect, I think that it would have been better for me to do it by self-study.
- Will it be difficult to have a hypnobirth if my toddler will be present while I am laboring? (he'll have someone taking care of him, but still)
If you master it well, then no. You'll be able to filter most things out. Although as the mother of a persistent toddler, I'm beginning to have my doubts!
Anything else I should know about hypnobirthing?
My main peeve is that I don't think the book (or my instructor) prepared me well for the pushing phase. It wasn't completely clear how she (or Marie Mongan) wanted me to breathe for it. And how the #*&^$%# was I suppose to continue visualizing a calm forest while
pushing??! Seeing as I ended up pushing an OP baby for 4 hours, a little more preparation would have been nice. The experience was also an unwelcome reality check from all of the peace-love-babies stuff that I'd "learned" in class.

: (This was my first baby).
The actual course included a lot of videos of women using the method and just *sighing* to "breathe their babies out." Yea. Whatever.

Suffice to say, my opinion of the program is only ho-hum, but maybe a different instructor would have made the difference.
This isn't your first baby, at least, so you'll probably go into it with more realistic expectations than I did.