Hi Thommo
The names are not super common so it may be relatively easy to find them. I know little about where one lived on the canal boats (I am in Australia) but I have found these records on FreeBDM which are possibles
Birth Dec 1909 Fereday Alfred William Wolverhampton 6b 579
Birth Sep 1913 Macdonald Evelyn Evans Wolverhampton 6b 1198
With a birth on June 20, they could have missed the Jun Qtr

The mother's maiden name is Evans (for Evelyn). Was Jennifer Whitehouse your g grans maiden or married name? I've been looking for a marriage of a Jennifer Evans without success at the minute. THe marriage certificate for Alfred and Evelyn might help with names
Edit: Obviously your g grans married name was McDonald - sorry for the question - either she was previously married or the birth above for Evelyn is not correct