Honestly I would quit both. You stated that you don't need to work, you just want to. I get that, but the thing is both jobs are putting undue stress and strain on your family. It would be one thing if you had to work, but that's not the case here.
Is your 5 yr old in school? If so, I assume he/she is about to be on summer break. I would spend the summer taking care of them, plus maybe that will allow for travel to see daddy more. Then say about mid-summer start looking for a part-time day job, so that when the school year starts your oldest will be in school and you can put the youngest in day care part-time. Work while you have the free time. Or check with your local school system, in my area they have pre-k3, pre-k4, pre-k and then kindergarten. It's free cause truthfully its school, but not stressful, kinda like advance daycare.
I have to say again since you don't have to work, you should just stay home until your children are older and it becomes easier. You have an ideal situation where you can support your family without making a lot of the sacrifices many of us have to make.
However, if not working is not an option, keep the restaurant, quit the gas station.