I'm so sorry your going through this and I hope everything works out for you and your babies. I can honestly say I understand your situation and I hope your ask lucky as I was and get to keep your babies. It doesn't sound like you have been irresponsible at all. You are being very responsible to research and look at options IN CASE it comes to that. An irresponsible person wouldn't even take the steps you are taking and would just turn them loose or over to a shelter without any thought.
I'm very upset right now.

I have been in her shoes and if someone would have jumped on me I would have been even more devestated than I already was at the time. She loves her babies and doesn't want to have to give them up. She hopes it doesn't come to that but is being a responsible momma by looking at options now in case it does unfortunately come to that. Shame on you for jumping on her that way. None of us can fortell the future. Sometimes life just throws us a curve ball and we deal as best we can when that time comes. There are many people that have had to give up their children (skin or fur) due to unforseen situations.
If I had gone through life planning for the worst case scenario I would never have...
... given birth to my oldest child because his father and I later divorced causing him to be from a broken home. Oh and don't let me forget he has a medical condition. I should have seen that coming too.
... gotten married the second time and had another child because it could end the way the first one did in divorce. Everything is good but hey, I should have learned my lesson right.
... purchased a vehicle on the off chance that I could be involved in a hit and run accident that was not my fault and not be able to financially fix my vehicle right away and my deductible is above what it costs to fix it so no help there.
... gotten a job because some day I might just loose it by being fired or layed off. I could just live off the system and get food stamps. That way I won't have to adjust to a new lifestyle later on. Savings can only take me so far then I'm screwed.
... purchased a home because some day I might just loose my job and have it forclosed upon leaving my family homeless, or forcing me to live with relatives until I can get on my feet again. (Thank goodness living with my parents was an option for me when I got divorced or I would have lost everything.)
... ever been born because who knows what's going to happen around the corner. Maybe my parents should have thought better about going through with having their 'accident' and not had me at all. After all I have had a few bumps in my road of life. They could have saved me from all of that. What were they thinking!!!!
Your right... I should have planned better just as you suggested the OP should have done!
For situations such as this I have learned to 'never say never'. Karma has a way of sometimes coming up and biting you on the backside. I agree that there are irresponsible people and your level of frustration with that would be warranted in those situations but it doesn't sound like the OP is one of them. It seems she is trying to do her best but prepare for the worst case scenario if it comes to that. She could easily wait until the last minute and drop them at the pound if it came to that but she's not. She is researching options IN CASE. Save your anger for someone that deserves it because this does not appear to be one of those cases.