A good size for mini hoops is probably anywhere between 18-26 inches. I think the average is 22-24. Hoopnotica has a new minis DVD that's $20 and starts with some really basic moves and Home of Poi has a beginner poi DVD that's only like $6 or $7 but I'm not sure how it would transition to hoops (I ordered one last week). I haven't taken any of SaFire's online classes but have heard great things about them. I've also used some of HoopDeeDoo's tutorials.
When I first started hooping I didn't think I'd ever have an interest in minis, but now that I'm getting into them I love it. I can only do a few moves so far (chase weave, windmill, and what Hoopnotica calls flag pole; I'm working on thread the needle, three-beat weave). Anyway, it's why I ended up ordering a set of flag poi too. I feel like learning both will give me more room to play and practice. :)
I have a few mini tutorials.
If there are any other moves you want explained, let me know!
http://www.youtube.com/watch?v=BeU7ZAHrAJo Forwards 3 beat weave
http://www.youtube.com/watch?v=rjMKkW1h67E Backwards 3 beat weave
http://www.youtube.com/watch?v=j3aLwN3YIeI&feature=related Timing and Direction