Irish birth for both of them as you thought

From the 1871 census:
Daniel McWilliams 26 labourer b. Ireland
Mary Ann McWilliams 25 b. Ireland
Daniel McWilliams 4 b. Glasgow
Thomas McWilliams 1 1/2 b. Glasgow
Daniel Murray 16, Sailmaker, brother in law b. Ireland
Frances Murray 13 Cabinet Maker, brother in law b. Ireland
Peter Fairey 19 boarder b. Ireland
Edward Gillon 22 boarder b. Edinburgh
Address: 63 King Street, Tradeston Glasgow Govan
Some children showing to them on IGI:
1. DANIEL MC WILLIAMS Birth: 18 APR 1867 Tradeston, Glasgow
2. THOMAS MC WILLIAMS Birth: 17 SEP 1869 Tradeston, Glasgow
3. ANNIE MCWILLIAMS Birth: 15 MAY 1872 Tradeston, Glasgow
4. JOHN MCWILLIAMS Birth: 18 OCT 1874 Hutchesontown, Glasgow
Regarding Daniel and Mary Ann's birth place in Ireland, you might be fortunate and find that they gave more information regarding where in Ireland they were from on one of their census entries.
Monica