A holiday trip after taking lomustine?

So my dad has been diagnosed with Glioblastoma since November 2023. The surgeons were able to remove the whole of the tumour. He’s had Radiotherapy and Chemotherapy then about 6/7 months off treatment. The tumour has started to grow back viciously and he’s turned down another craniotomy due to how traumatising it was last time. The doctors have said he has a few months left. He will be starting Lomustine hopefully in about a week.

We are thinking of a last family get away to a seaside but unsure how the Chemo tablet will affect him. Do symptoms come straight away or few weeks after taking? We are hoping to go away in 3 weeks for 4 days

EDIT: He’s currently had a chest infection with potential air in his lungs for about 6 weeks now. Which is delaying Chemo because it needs to clear up before starting it