Its great to read that you are researching the breed and preparing yourself as much as you can.
Firstly you have definately come to the right forum as there are some great people on here who will always offer advice.
I was in the same situation as you i.e first dog and 2 kids (mine slightly older than yours).
Mine cocker Jett is 10 months old now and I got him at 9 weeks old. We went for a cocker because I wanted a gentle family dog that was clever and had enough energy to go running with me.
We definitely got that, he is absolutely nuts
but at the same time he is completely harmless. He loves the kids so much and will happily play with them for hours.
I must admit there has been times when its been hard but i'm now at a stage where he is just amazing.
I have crate trained Jett, he goes in his crate at 10pm and will sleep through the night. I know some puppies are fine with this and it will only take a day or so to adapt, this was not the case for Jett. He was a royal pain and at first, he hated it and cried and barked constantly. Obviously with kids trying to sleep it was stressful times.
However with help from this forum I realised what I did wrong. I orignially got him the biggest crate you can buy, my human mind felt that he would like the space. I also put water and food in there. Both these choices were a mistake on my behalf. I got him a small crate so he felt snug and made sure he had water before bed, I also covered the crate with a blanket and put a clock next to the crate. He then loved it and started to relax and he slept well.
Jett then started to grow and a few months later he started barking and crying again. I then made the decision to change his crate back to the big one. He is now happy again and just loves his crate.
Puppy training is definately a good idea as it gives the puppy the basic commands.
Another thing I picked up on is when Jett rests I tell my kids to leave him be and the kids are not allowed to play with him in his crate. The crate is his area and its not play time when he is in there. When Jett is tired he does naughty things so we make sure he gets his rest.
He gets 2 walks a day, normally one in the morning for an hour and another in the evening for 30 minutes. He probably would be fine with 30 minute walks but we are just in a routine and we like to get out.
Sorry one other thing, when we needed to go out and leave Jett we got a puppy play pen which was very good and it kept him safe and at the same time enough space for him to play and run around.
Good luck with it all and keep us updated.