help with multiple secondaries

I have a 5 gallon extract american stout that has been in primary 3-4 weeks. What i am wanting to do is seperate the beer into 3,4, or 5 smaller batches and experiment with different ingredients (vanilla, chocolate, etc.) during secondary.

1. Is this wise to do? Does it effect the integrity of the beer when you break it down like that?
2. What are some ways to go about doing this? use precious carboy space or will some other container work?

In theory you could use anything that you could attatch an airlock to. Do you have a bunch of growlers sitting around? Now would be a good excuse to buy some. Your LBHS should have gallon jugs which would make it easier (fewer bottles). As long as you siphon without splashing you won't really have to worry about oxidation but taking it out of the primary and putting it in a bunch of bottles means it has greater potantial to get light struck. Just keep them covered.

Gallon apple juice jugs work good, and you can make some Apfelwein or some Graff.