Basic ReadyNAS, Samba 4, AD and NFS setup question

OK - so I've got a ReadyNAS 312 configured to use AD authentication (against a CentOS server running Samba 4.1 as the AD server). It works just fine if I try to mount it via SMB or AFS from a client machine. But if I mount it via NFS on another Linux box, the UIDs are mismatched. In hind sight, it's obvious why they shouldn't match, since uid/gids are set locally on the client NFS box, and in Samba on the Samba server. So my question is this - what do people do to solve this problem?

Are there tools one can use to set the UIDs/GIDs in Samba to those that already exist on the Linux server? Or conversely, is there a way to dump the username->UID, groupname->GID mapping from the Samba server so one could go in and set them on the Linux server? Or is that a silly question (i.e. do AD users/groups have UIDs/GIDs that are of a different form/range than Unix UIDs/GIDs?) It'd be painful to have to pre-set everyone's UIDs when users or groups are created, but I suppose it happens infrequently enough I could do it. But some automated mapping tool would be easier.

I know this might not actually be a ReadyNAS question - since I guess this would be an issue regardless of whether I had the ReadyNAS as the fileserver or some other type of file server. But maybe this is a common setup for ReadyNAS AD users and so the answer is easy.

Thanks!