You can search each child further on familysearch.org. https://familysearch.org/
This census gives birth month and year for each.
https://familysearch.org/pal:/MM9.3.1/TH-266-11901-172071-85?cc=1325221
1900 Census
Head Patrick Buckley M 46 b Mar 1854 IRE immig 1859
Wife Annie Buckley F 44 b Sep 1856 IRE marriage abt 1874
Daughter Mary F Buckley F 24 MO
Daughter Lillie Buckley F 21 MO
Daughter Anna S Buckley F 19 MO
Daughter Agnes Buckley F 17 MO
Son John F Buckley F 16 MO
Son Charles C Buckley M 13 MO
Son William M Buckley M 12 MO
Son Leo J Buckley M 8 MO