hi, and welcome, Lindsie, I haven't posted on one of your threads I don't think, so please let me say WELCOME on this one!
There is NO difference in using Labs vs Poodles, for sire/dam.
My Sheba is a 45lb 24" Std. POodle, and she gives us 12 healthy babies almost every time!
My personal theory is that Lab breeders could switch/do both Labs and Doodles by keeping females and just buying a male poodle, but that's just an observation or theory.
My vet said that the size of the sire has no bearing on the size or ability of a female to deliver. He was a vet for a horse breeder and cited studies they've done with horses. But that's what he said, if it helps.
As for your loss of your f1 girl, I'm so sorry!!!
Oy, our 8 mos. old Truffle got out and was lost for 4 days and I was really dreading finding her body on the side of the road somewhere, when thanks be to God she was found and came home. So I'm afraid I had a happier ending than you but I really can imagine loving your doodle and having such hopes for her, and the sadness of it all.
Our kids are young....my baby girl is 10 and ALWAYS sheds tears when one or two of our puppies leave....but it's her loving on them that makes them such sweethearts, I'm sure of it, so I encourage her and hug her a lot. Your 6y/o son will be a very valuable asset to your puppies and your reputation with others, I'm sure of it.