I was juuuust about to pile in with #TeamCavy but you're going with rats (good choice)
I loved our guinea-pigs , when my DD was 9yo she wanted "A Pet" , I said "OK , but guinea-pigs " (because I kept them from 9-22yo myself .
She wanted a boar.......we got two brothers from Rescue . Then got into The Spiral of one dies-you get a new cagemate .....we had 8 over 8 years .
Train them? No . They are sweet , gentle ,huge characters . Greedy and Nice-but-Dim.
Let them free-range ? Nope . Not safe for them , they need protected from everything as does everything from their teeth.
My DD was brilliant , we did the pig care between us because half the pigs were mine . But there were days she was ill , away or too busy when it fell on me (or DH if I wasn;t available)
They are messy . Hay gets everywhere (and hay & fur are huge allergenics for children) . They do pee/pooh a lot but it doesn't smell. Hay does .
They are prey animals 100% . Some are very laid back (our boars were) some more timid . But they are rodents and they can bite but rarely do . Usually if a guinea-pig bites you it's an error (your hand smells of food) or you've upset them. I had a mouthy rescue but that was her . She wasn't a childs pet .
And they get ill and die suddenly . Very little chance to pull them round .
We had a gorgeous piggie house made from my DC old wooden playhouse . In winter they had the small bedroom.at night time
Their last winter we kept them in all the time as they were getting old .
My DH wanted a cat/s , so once our herd decreased over time till our last guinea-pig died .
I have to say cats are easier . They are in charge of themselves . We don't need to put them in/out . They have a microchipped door .
Ours aren't cuddly but like to sit on chairs or beds .
You could get a cat that is proven to be a proper LapCat . Ours aren't but we knew this before so I;m not offended .