There's an old saying, that you never argue with the family in front of outsiders. If word of this gets back to the VC, it will make your team seem weak and indecisive. In fact, the VC shouldn't have been telling you guys how to split the pot...You should have been telling THEM, what the team already agreed to.

That being said, CEO and the CTO should be getting greater equity share than junior developers. At the end of the day, the buck stops with you two. You should be compensated accordingly. Even 25% split across the board doesn't reflect this.