Change in drivetrain possible?

I have a Genesis Croix de Fer with Tiagra 4700 (50/34 front, 11-34 cassette).

I need to replace the cassette (worn) but the supplier is out of Tiagra 10sp 11-34, however they have the same in 11-42.

I am getting old and would surely enjoy the 42 when climbing (of course at a price of harsher...