These bits and pieces I am giving you at the moment are for THIS SPECIFIC TIME in your journey. From what I read.. in 2 months, 6 months, a year, it may change but for now, this is what i see.

Kids are like sponges. They suck in info from all around. They are curious and want stimuli about everything. In an healthy environment, surrounded by good role model, they will take in great insight on how to become themselves great adults. They need the same things we do. Love, shelter, food, clothing, care ... My therapist had mention, regarding my personal situation and my Ex-H' s state, I had to be the BEST me I could be and keep myself grounded so that my children would have a good role model and strong root system, regardless if Ex-H came back or not. The children interaction with their father was an open door and I stayed out of it unless my children got heart emotionally.
( I have 4 kids.. age 6,8,9,13 when he left.. 7 years ago, due to MLC and depression )

"They don't ask about their father much and somehow they got used to him not available no more.".. It is telling me that they are getting everything they need from you !!! smile Congrats!!!

Do not stand in between them and him.. ( and I can see you are not ). Let him take his responsibility as an adult and father OR he can live with the consequences of HIS choices..

In my opinion, you are succeeding in regards of your parenting. smile I am very proud of you..