always speak to the consultant for advice

everything will depend on treatment plan.

You could enquire about putting holiday back a little to give you some time to deal with treatment.

if you didn’t disclose health problem to insurance before diagnosis,  then you’re likely to loose your money if you leave it till within 12 weeks of travel. 

I had lung cancer twice.

First time full lobectomy upper right lobe. Surgery only treatment and was aloud to fly after my surgery follow up appointment with consultant which was about 3 months after surgery. 

second time,  I had surgery end of  November and chemo January till April. Had half lobe removed on left side ( lingulectomy ). Traveled end of may. 
didn’t have any problems 

maybe move holiday.
 Hopefully  surgery alone will be sufficient to resolve cancer without need for further treatment- allowing probably the option for an holiday to recoup 

if further treatment is needed you could always move it again

I had moved my holiday once the first occasion and three times on second occasion of cancer, without any charges, due to doing it before 12 weeks of travel.
 I wish your husband well with his surgery and recovery and being able to have something to look forward to will certainly help you both through this 

I hope this helps x