For the history:
http://en.wikipedia.org/wiki/Romanian_War_of_IndependenceHe could have worked for the Danube and Black Sea Railway Kustendje Harbour Company.
http://www.maidenheadphilatelic.co.uk/index_files/levant.htmIt was a British company that operated from 1860 to 1882 (when it was taken over by the Romanian government). It would fit with his occupation, in 1881, as "Engine Smith".
familysearch.org shows:
Charles (b. 25 Mar 1871 chrs. 21 May 1871)
Julia (chrs. 04 Aug 1872)
Annie (chrs. 09 Nov 1873)
I'm not sure the children were actually christened in Bucharest, the source numbers track down to baptism records from the British consulate, and they've been tagged with Bucharest as a location, but there appear to be records from multiple sources on one film. It wouldn't be the first time the location on the familysearch index was not quite right.
The consular birth indexes show, in 1871-1875 births, all three children as registered at Kustendjie
Charles Robbie, vol 5 page 1889
Giulie? Robbie, vol 5 page 1890
Annie Robbie, vol 5 page 1891
and in 1871-1875 deaths
Giulie Robbie, Kustendjie, vol 5 page 1901.