Do what`s best for the rabbits couchy. Rabbits can be a really big commitment both in terms of housing and expense. They need a very large cage indoors (like a large dog crate converted for them) or if kept outside, something like a small garden shed to live in and a large attached run so they can run around and do bunny things. As far as I`m aware, they also need speyed (as has already been suggested) and injections each year against disease. Your vet would tell you more about those.
Their diet needs careful attention aswell because their teeth can suffer if they are fed the wrong diet. Pelleted food is the best and good quality hay at all times. Never feed cut grass as this ferments in the stomache. Nibbling grass from a lawn is fine though.
Rabbits should always (where possible) have company, so your pair are already bonded, which is nice.
The best way to find rabbits a good home is to join a rabbit welfare forum and not rehome them as kids pets where they might just be kept in a small hutch in the garden and their welfare needs not met.
It`s a shame your mum and nan are not a little more sensitive to their (and your) needs right now so try and make them aware of this and that you just can`t get rid. If they go back to their previous home, they might just end up living in that small cage. If they were unwanted there, they will probably be handed on again to someone else who isn`t rabbit savvy and that would be a shame.
I hope you are allowed to keep them at least until a home is found that is suitable.
Good luck.