Cycing that far North in late April is still winter. Snow showers, freezing rain, and ice-cold arctic winds are all possible.

You will have to skip Andøya and head to Harstad, where there are few ferry options to get over to Senja and join the main route. The benefits of cycling in late April or early May are the roads will be quieter and accommodation will be cheaper and available at short notice.

Here is the route I recommend: https://ridewithgps.com/routes/46110518?privacy_code=m1FQ1p9beukiGBUzLA3AMcOkFWlxqfOV