Tin will have a higher ionisation enthalpy compared to lead because in the periodic table, tin is palced above lead in the same group. This means that the size of the atom in tin is smaller than that of lead (atomic size increases down the group). 

Yes. Ionisation enthalpy is related to the atomic size. The greater the size of the atom, the farther will be the electrons from the nucleus. Due to this, the nuclear effect on these electrons will be less, and it will be easy to remove such electrons when compared to an atom having smaller atomic size.