
Sadly Beth I do feel you have left it rather late.
A five year old Lab bitch that is overweight too is not a good breeding prospect, and you could evn loose the bitch during whelping, as a bitch needs to be hard and fit to bree4d from.
She would need to have her Hips and Elbows x-rayed by your vet, and the x-rays sent to the British Veterinary panel for scoring, and the results would need to be good. Also Lavradors should have their eyes checked Annualy, and have a certificate in the current year before mating.
There are already 36,000 Labradors bred, some of them very poor quality and bred by Puppy farms.
In breeding your main aim should be breed improvement. You would need to know if your bitch is an outstanding example of her breed. It doesn't always follow, but you would expect to see quite a few Champions or Field Trial; hampions in her pedigree if she has been well bred by a breeder aiming to improve on their breeding.
It is very easy to be anthropomorphic, but really what she has never had she will never miss. Even though she seems maternal, ypou never know until a litter arrives if the bitch will be a good mother, and an older bitch that has been a spoilt baby herself may often show conflict between her duties and her attqachment to the family, and neglect her offspring.
If her breeder is a good breeeder then she will be able to advise if she is of sufficient high quality as regards the breed standard. I take it as read that her temperament is exemplary, and I suspect that she is yet to have the above mentioned health tests, so her status in this area is unknown.
You mentioned you have a puppy. If after study you think breed advancement and breeding are for you, then maybe, if tyhe pup is a good one, you could have a go at showing it, and get an idea of what the requirments in the breed are. Then some time down the road you could purchase a top quality bitch pup from lines you admire, and get into this mad world of breeding dogs.
Hope that helps!