Book composition and cover design based on a drawing

Hi talented people,

I need a graphic designer/illustrator/folder in one. The assignment is for a musical children's book of about 10,000 characters. My illustrator friend, created the drawings (16 pieces), but by hand on paper. They are scanned (600 dpi), not sure if it's better in pdf or png/jpg. They are black and white because that is the idea of the booklet. I'd like the drawings to be nicely integrated into the text, not caniacally surrounded by text. In addition, every few pages there will be contrasting pictures - I have prepared in canvass as much as possible, so it will be easier to see what I mean, but I want the contrasting pictures (based on the pattern) to be given by the graphic designer in a style that will fit the whole. And the last topic - the cover. Here there will probably be more work, because I also have only a drawing, it needs to be adjusted graphically and colored somehow ... Dimensions of the booklet will probably be B5 eco (165x235) but I will still agree with the printer. Composition of the whole both for print and ebook. Best regards and I hope that the project will work out. If it makes it easier for someone to estimate, I can send a sample drawing.