Does the oxidation for all the aliphatic monoaldehydes to carboxylic acids have the same value of electrode potential?
My answer to your main question is no.

Firstly, you are simplifying the process of oxidation of the monoaldehyde. The mechanisms for oxidation depending on the oxidising agent used, although they are generally the same (Refer to link). By considering only these 3 bond formation/cleavage events, you are not looking at this process in totality. 

Secondly, the side chain does matter as it would affect the bond energies of the bonds that are broken and formed. Different side chains may give the aldehyde different steric strains etc. Depending on whether it is more electron-withdrawing or electron-donating, it can severely influence the bonds on the carboxyl group. 

Due to the variations in oxidising agent, medium of reaction and side group of aldehyde, the oxidation of different monoaldehydes to carboxylic acids would have a different value of electrode potential as these factors would affect the feasibility and ease of oxidation. 

Oxidation using chromic (VI) species:

http://www.chem.ucalgary.ca/courses/350/Carey5th/Ch17/ch17-3-5-1.html