Read As Written, I suspect not, as each makes implicit assumptions that the Aid Another action grants +2, and neither is phrased as a bonus so much as a change. The OOTD ability describes the higher level increases as bonuses, in a sense.
Read As Intended, I doubt there's reason not to stack them, but the awkward wording offers little to support it.
I agree with macksting - I don't believe they would stack. I might stick with the Halfling Helpful trait and go with Order of the Shield. The Helpful trait should stack with the extra Aid Another actions you can take with Bodyguard and the +2 DEX bonus will help you get more attacks with Combat Expertise.