I have a lab that I got from a resuce centre in the north west as a puppy and they rehomed it with my two small children. They did want to know if we had, had dogs before etc. . Sorry can't remember the name off hand but I'm sure if you google north west labrador rescue you'll find it.
A lab puppy is fine so long as you take it to regular puppy classes (good recall, lead training and basic commands). I found that I trained him to not jump up at people within about a week. Just turn your back and don't engage with them labs dont like being ignored and soon learn. All this talk of your child being knocked over by a Lab is IMO a bit weird. who in there right mind would let there 1 year old who I'm guessing hasn't been walking that long alone with a dog? or alone at all for that matter.
You've had a springer, so you have an idea of the ammount of time you'll have to spend walking a lab we're talking three 1 hr walks a day min and a big back garden. The problems set in when you don't offer them enough constructive excercise they will chew if you leave anything soft around so a puppy training cage is one solution. I used this then later let him sleep etc. in the kitchen. loads of pot and pans precariously propped over the bin will deter them from emptying the contents over the floor. you don't have to do this forever just untill they stop doing it...
Labs are very chilled out if a small child say pokes them in the eyes or pulls their tail they just move away...rubbish as a guard dog though unless a theif was alleric to being licked
Costs
I feed my dog on a dry working dog food becuase it's high in potein and is vat excempt this is £15 / 15kg sack and that last 30 days. there are cheaper and much dearer options
injections are £20/year
Puppy classes £7 per week about 4/5 years ago so a little more now I would think and dependant on area.