The actor is father to James Padraig, 8, from his relationship with American model Kim Bordenave, and Henry Tadeusz, 2, his son with Polish actress Alicja Bachleda-Curus.
"One of my sons loves footballs, tennis balls - anything round - and the other is mad on trains," Farrell told The Sun.
"Toys keep them happy and I give them ice-cream - that's about as extravagant as it gets.''
The Total Recall star tells Jonathan Ross tonight: "They give me a will to live that's greater than my own desire to see my days through. To see my days through with them is pretty cool."
Jessica Biel recently revealed that she was constantly inspired by Farrell while the pair were shooting Total Recall.
Watch a clip of Total Recall below: