Be very careful. Depending on the local authority, the option to go on the waiting list varies. For example, in some London boroughs you CANNOT go on a lower preference school waiting list. For example, if say, you got choice 3 of a possible 6. You could not go on the waiting list for schools numbers 4, 5 and 6, but you could go on the list for schools in positions 1 and 2.
I know, for example that this is not the case in Kent.
In that case, you would possibly be able to go on the list, but only by making a fresh (and therefore late) application for a place at the school. If you had already made an 'on time' CAF submission, the LEA would certainly not accept that you could not have made a timely application with the schools in what you have now decided is the preferred order, if you see what I mean.