I agree entirely with @vanillandhoney, I also dont think you should go on holiday and leave your puppy when they are so young, or at all really if Im honest.
Far too many people think only what a dog has to offer them and not what is in the best interests of the dog. I have seen it time and time again with my fosters, people are happy to accept the dog`s love, loyalty and devotion, but do not offer the same in return.
I am not saying this is the case with you @Guineapigbridge, but it is not in your puppy`s best interests for your to go on holiday without him.
There are very few dogs who actually want a doggie friend for a sleepover, is would be highly unusual to find one who liked it, even if some tolerate it.
Playing with other dogs is different, but to have another dog and person staying in his house when youve gone and he doesnt know where you are or if you`ve abandoned him?
It would be slightly better if the dog sitter didn`t have a dog, or better yet was an insured professional. I would not put my dogs in kennels either.
As Vanilla says, whos going to pay if theres an accident? What if this causes behavioural issues in either dog? Who`s going to pay for a behaviourist?
Do you want to take the chance of your puppy, who it sounds like you are doing a great job with so far, developing serious and potentially lifelong issues? Reactivity to other dogs? Resource guarding? Anxiety? Separation anxiety?
As I said before, I am not the best person to comment, our dogs always come on holiday with us, and I cannot imagine leaving them behind, it would upset me too much.