Can two new rabbits get on with my current rabbit?

you cannot just add a rabbit or 2 and expect they will all get along. Trios firstly are very, very tricky. Even the easiest to bond combo spayed/neuterd female-male can be tricky. Betty will likely react as them being intruders. Rabbit bonding is something that needs to be done under strict supervison in small netral space and it does take time and patience. I don't see how you can have an 8th acre of bunny proofed land as domestic rabbits are from wild European rabbits and burrough also they are not protected from perdators both 4 legged and winged.