Hello Yvonne
Late in the day I know but I've just found your request for the children of Richard & Alice Mercer.
I have the Parish records for Deal and on 7 Nov 1903 Richard Dick MERCER, 24, Waterman of 33, Water Street, son of Richard MERCER, Boatman married Alice Mary BLOWN, 24 of 1, King's Arms Cottages daughter of William Thomas BLOWN, Labourer.
Witnesses were Lavinia Elizabeth MERCER & Richard SAUNDERS
I have been through the records of all threee churches plus Roman Catholic, Wesleyan, Sholden and Walmer and there are no baptisms recorded for Richard & alice MERCER. This suggests that, if they had children, they moved away or the children were not baptised, which is unlikely.
I am sorry I can't be of more help
REgards
AJ