I know under 2s go free as they have to sit on your lap. My dts will be 2.6 yrs when we go to lanzorote in may, but they were 7 weeks prem and still tiny for their age, so will not be able to sit in a seat anyway. Do they allow them to sit on your lap after the age of 2 so you dont have to pay for the extra seats.
Not been abroad with the kids before, so have no idea.
I dont know if it makes a difference, but we want flights only as we will be staying with my parents who live in Lanzorote.