It would make sense to me if the local schools actually joined forces on this and rotated the location so that the burden of hosting is shared. Of course, that would depend on the numbers of children joining the code club.
Also, that's assuming that the CRB check applies to the Code Club and not the school. As there's no national CRB register, if the CRB applied to a specific school then you'd need one for each location. If it applied to the code club then you could carry it between locations.
When I was CRB-checked for the junior rugby club I recall vaguely that you don't need a CRB as long as there is someone else present who is CRB-checked. That might just be me making it up though!