Leaving 15 week old for ~5 days, will he hate me when I get back/what to expect?

Hello, I have had my 15.5 week old puppy for over a month now.

I am a recent college grad and so he has traveled with me a lot (stayed week+ at various family's homes and hotels, as well as my apartment...but always with me there).

I have to fly across the country and a family member will be watching him for five nights. They have a middle schooler and two adult dogs who tolerate him. He has stayed at their house one night before (with me), two days ago (I thought it would help prep him for my trip...).

He is crate and potty trained (for the most part). He goes in his crate easily to sleep and doesn't whine. I have been able to be with him pretty much 24/7 the past month and we have made so much progress in training (crate, potty, and commands). He gets along well with any dog (including the two he will be staying with) and is generally a happy, obedient puppy.

I am so so anxious that him staying 5 nights with them is too long, and that it will have lasting negative consequences, such as separation anxiety. I understand they may not keep up with his training like I do because they have lives and other dogs, so I expect a little regression there possibly to work through after. However, I really fear this experience being detrimental to our bond.

I will bring all his things (food, toys, crate+bedding+sound machine) as well as letting them know his potty schedule.

TLDR; looking for advice, reassurance, or personal experience with this sort of thing.