This looks like a possibility for Peter in 1881, -
Peter SMEATON, 37, Carter, born Auchterarder
Jane SMEATON, 39, Wife, b. Dunning
James SMEATON,13, Son, b. Auchterarder
Jane CROW, Lodger, 65, b, Auchterarder
Jane CROW may be related in some way, but, from this Peter's marriage record, it's not his mother-in-law !
But are you certain that you have the correct parents for your Peter b. ca. 1844, as the above Peter's likely death and marriage records in relation to the 1881 census record don't show them as Matthew and Margaret CALLUM ?
Things get a wee bit complicated in the sense that there were two Peter SMITTONs, both born in Auchterarder parish in 1844, one on 01MAY1844, the other on 01OCT1844, the respective parents being Matthew SMITTON and Margaret Callum, and William SMITTON and Jane[t] FAICHNEY.
Note that they are very probably related, both being named after their paternal, even but less likely, maternal grandfather in conformance with the widely used naming patterns in Scotland.
kirkmichael