Aeration should be done ideally spring and fall when the air temps are cooler. Aeration exposes the roots which will get baked in the summer heat.
De-Thaching: I would only de thatch as needed. When the "thatch", (found below the mulched clipping and dead crowns) is more then 1/2" thick its time to de-thatch. Using good lawn care practices, you should not ever need to do this.
Power raking: Is something I do yearly in the spring for many people. It is just a light rake of the surface and the accumulated clippings and dead crowns. I think its unnecessary to do this for any other reason then visual appearance, much like some people are unwilling to deal with mulching their grass and therefore it must be bagged, visual appearance. I only do power raking after explaining to a customer that they do not need it, and if the still want it done, then I will do it, cause hey if I don't someone else will.