Two dogs here, although I only had Kip for a year before Whisky came along.
Even though mine are very similar in age, size and breed, they are totally different characters. Again the introduction was a bit mheh, ok in the garden, Kip very subdued and defensive in the house, I don’t think Whisky dared to lie down in sight of her for a week (although no actual fighting).
It all settled down very quickly, they both obviously look out for each other when out, and play well outside. Kipper is much calmer and seems happier with Whisky about, but there is still a dynamic between them, no shared beds or spaces, no curling up together.
I’m trying to say, as above, if it was going to be a disaster then Bloss would have made that clear. The dogs will form a bond, but it might not be as close as you imagine (or not obviously to a human) but I honestly think the dogs both benefit from the extra companionship. I would never go back to one dog, although I appreciate that the age of your Bloss could make things a little harder for her. It sounds like your whole family will look out for her, and not just get excited about the pup, which is brilliant and I’m sure will help.