Beans and Onion Sets will be fine Alder, but not seed potatoes as they will get Thrips and be ruined.
Seed potatoes should be planted in land manured last September.

For runner beans dig out a good trench and put anything eg rotted manure,compost or compostable into the bottom. Some folk even use veg peelings or shredded newspaper but others are wary of modern printing inks. The idea is to get a reserve of good moist stuff for the roots to grow down into. There is less worry with beans about unrotted stuff using up nitrogen as beans can extract their own from the atmosphere. And no its not too late.

Runner Bean roots are very short.