You've had loads of advice from others on your breeder and what you have in store, so as another mum with young children I'll give you my perspective
Firstly, HUGE hugs from me. I have a 1 yr old daughter, a 7 yr old son a 3 yr old normal easy-ish show type and a 5yr old very big rescue Weimaraner with a strong hunt drive, from strong working parents with a good dose of hormonal huffiness and issues with other dogs just for good measure
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It's hard work but oddly, no where near as hard as my first show cocker was. He was a very very busy hyper dog with a very strong hunt drive (he'd start shaking the second he caught a wiff of any game) and endless energy, he was impossible to wear out - I can honestly say, the only time he relaxed was about midnight for the night or if he was cuddling us. He was also my first dog so I was on a learning curve with him and I'm sure made loads of mistakes... but he had the most amazing happy loving temperament, was perfect with my son and he was the dog of a lifetime for me and I'm still in pieces that 3 years ago I lost aged just six very suddenly.
Dogs like Daisy are very hardwork and they are more of a lifestyle than just a family pet.. but they really can be the most amazing family pets also.
You have an awful lot on your plate right now, particularly if your hubby is away a lot. Your children will be making your job of training/managing Daisy a lot harder than if you didn't have kids (this isn't said with anything other than fact and personal experience behind it - even managing my second 'easy' show cocker as a pup was a real pain around my then 4-5yr old son who was dog savvy) and it will also take longer for her to get the hang of things because of them. HOWEVER, although you are facing a very very difficult year or 2 until your youngest goes to nursery, when she does, that will also coincide with daisy growing out of her difficult 'teen' months and also being able to do more exercises and suddenly you will have a bit of time together where you can really cash in on the little brainbox you have and develop an amazing relationship and continue to be amazed at what you can do together
Your husband is right, you do have to put the kids first because otherwise you will end up beating yourself up and in tears that you're doing everything badly but if you can fit a structure into your routines for the next year and a half that gives Daisy some regular quality time with you focusing and learning then although not ideal, you could make it work.. For example, keep Daisy somewhere confined for periods of the day so you can play with the kids or get on with other things and she can relax and have some down time, then when your little one is sleeping do a couple of 15 min sessions with Daisy without your older child 'helping' so you can both focus and learn together.
She does only need short bursts of exercise at the moment which is in your favour but it does need structuring and you can also focus on exercising her mentally by training her to do things around the house - hide things for her to find, train her to fetch things for you etc etc...
Lots of people are offering help so chat with them and see if you can come up with a realistic routine/structure etc around your children and if you think you can manage it all... I wish you lots and lots of luck with your decision