BTW FWIW I have friends that own daughsunds and while they are very cute and entertaining in their own way like most small dogs they are hyper and can be quite a handful.
Seems unreasonable for them to want to impose on you to put up with rocky.
Let me expand on the eight foot Boa constrictor idea... maybe you could borrow one from a pet store or local zoo. Then meet your nephew and rocky at the door with your new pet and introduce him as Bullwinkle "I'm sure the two of them will get along just fine"