I always suggest using all your choices on the CAF, irrespective of being sure that you have a place at any one school. Filling in choices 2, 3 & 4 isn't going to weaken your claim to being in -say - the top 120 for Pate's but better safe than sorry.
For instance, if there were 60 children with 'Looked After' children, statemented or pupil premium ranked 121 to 180 for Pate's, they would all be offered a place before they allocated any other places, so current rank 61 could end up without a place! The same could apply for any of the grammars (but not pupil premium). It is highly, highly unlikely, though - but for the sake of sanity, use all your choices.
The consequences if it all goes wrong and you haven't put alternative choices is that you'd be offered the school that has places left after all the other parents choices (grammar & secondary) have been allocated.
I've heard appeals where children have been allocated a place halfway across the county, with transport by taxi or parents petrol money paid - it does happen! Whilst people may be happy to ship their children miles to a good school, would you want to do same for a somewhat less-good school?
So there is no qualifying marks for pupils in this premium category?