splitting batch

Im currently making a brown ale and I want to experiment with a little bit of fruit flavor, but thats not what my question is concerning. I have to carboys for secondary fermenters so I was thinking of taking half the batch, leaving it alone and putting it in the secondary. Then taking the second half and racking it onto some raspberries.
Would this work ok, or would I get too much oxidation from the added head space?
Some more details....5 gallon batch in 6.5 gallon bucket primary, two 6 gallon (I think) carboys for secondary.
Thanks.

It shouldn't be a problem. There will only be oxygen in the headspace until it starts fermenting, at which point, the CO2 that is being created by the yeast (which is heavier than air) will push all the O2 out throught the airlock and blanket the beer in goodness.

Have fun experimenting!