If you're worried about oxidation after 10 days, you really need to RDWHAHB.
Leaving a beer on a yeast cake, the biggest threat is autolysis, not oxidation. Don't let that scare you away from extended primaries, it takes months before autolysis becomes a threat. I leave my beers in the primary for 4-8 weeks, and have never gotten even a hint of autolysis. Anything less than 3 months, you really don't have to worry at all.
As for the CO2, any time the yeast are eating, they're producing CO2. Even after they're done, some CO2 is still left in suspension, and it takes a little while for it to gas off. After 10 days, the yeast are still cleaning up after themselves. If you want to go with an extended primary, leave it for a total of 4 weeks, check the SG, and bottle or keg from there.