Look up the more common weeds you have and may already know the names of on www.thetortoisetable.org.uk that will tell you if they are safe or not. Or just look through the database and compare pics with your weeds.Maybe a baby is more fragile for this...When the times come I'll just post pictures so people can help me ID weird plants, I cannot wait to let my sully graze outside, there is so much grass here, I don't think she will be able to keep it short by herself tho...no im not talking about getting another sully lol, lawnmower will have to work too.
Oxalis, daisy, ragwort, buttercup are some of the ones I know are considered unsafe as is anything with a bulb or tuber.
TTT tends to be cautious, but so am I and happy to follow their guidelines.