If your parents' package is Gig 1, Ultimate Oomph or Volt they should be entitled to the pods as part of the package at no extra cost.
If they have another package the pods may be £8+ p.m. extra. Explained below (but there is a typo in 2b which should read ... (without Volt) not ... (with Volt).
https://prod.ctassets.virginmedia.com/uploads/Wi_Fi_Max_POST_21_JUL_2023_v3_059b6b25db.pdf
The pods are described as an add-on so should not create a new package by adding them to an existing package.
If your parents are moving to a different package (such as the top tier ones mentioned above) to get the pods then that would start a new minimum term.
We read regular stories on here of VM and its sales agents being very creative in order to start customers on a new minimum term so do check out exactly what your parents are signing up to.
Many on here would suggest that the best way to deal with wifi issues would be to put the VM hub in modem mode, if possible, and use your own networking equipment which you own and have full control over.