Ireland – Wild Atlantic way on a 2020 Cannondale Bad Boy 2. With a little modification, is it doable on this bike?

I'm thinking of using my commuting bike : https://www.cannondale.com/en/bikes/active/urban/bad-boy/bad-boy-2

I've changed the tyres to Schwalbe Marathon Plus.

I'm thinking of upgrading my Cassette to give me more gears as the hills will be hard.
I'm 44 and live in Donegal, Ireland.