What a wonderful thing to own! How big are they? Are they pencil or did he tint them too? How many are there?
As they were made so long ago, they are unlikely to be acid/lignin-free paper, so the first thing to do would be to preserve them using Archival Mist. This aerosol spray neutralises the acid and helps to stop the paper from rotting. It might also prevent further yellowing that lignin (plant material used to make the paper then) causes, but check the label for that.
You would choose your album depending on the size of the sketches. The standard scrap-booking albums are 12"x12" (most common), 8"x8", 6"x6" or 8.5"x11". Or do you have metric in Zanzibar?
You could mount the sketches on acid-free card-stock mats, and you could decorate around them. You might want to journal your memories of him, or what you know about the sketches. Dates are important if you have them, even rough date ranges, and details of relevant places if you know them.
You might want to start with an introduction setting the scene. You could type it on the computer and print it out.
Does that help at all? I could go on, but I don't want to overwhelm you.
Hello and welcome to SJ. Rosey has given you some great ideas. I would also suggest that you scan the sketches. You could then place the original sketches is an archival album and play with the scanned sketches if you want to get artistic without worrying about damaging them.
If you have any questions please ask. I look forward to seeing your creations.