The message
from "Rosie" contains these words:

I have a toddler and a medium-sized laburnum tree at the back of my garden,
which seems to produce a lot of seeds.

How poisonous are these seeds?

Poisonous enough, and attractive enough to a toddler, to worry about.

Would I be
best off getting rid of the tree?

I wouldn't. Cut the flowers off when they fade and there won't be any
seeds. It's not difficult and doesn't take long (done it myself; we once
had a house with a shared drive; our side had two laburnum trees and
nextdoor had toddlers who often played on the nice flat drive with their
little prams and trikes etc.)

You'd only have to do it two or three times before she reaches a safe age.

Janet.