Dear Warhawkmom,
You mention your son having flat feet and there has been a failed attempt to correct this with surgery. Does this mean your son has the ability to walk as you say his CP is mild? If he can walk is he in need of a walking frame?
If he is walking what experience has he had with insteps? I cared for a CP child who had very flat feet, but once he had insteps this made an incredible difference to his walking. Fusion of your sons ankles will inhibit somewhat various movements, but more info is needed about the extent of movement he has and what activities he is capable of and involved in.
I notice this is an old post, so I hope you are well and that your son hasn't had fusion yet. Sadly, I know how confusion it is for those caring for CP individuals to know what is the best thing to do at times; and the 'professional' can be far from helpful.
Agape,
searchingsam.