I would carefully drill small holes down into the cracks, to give some grip, then fill with a slightly thickened regular epoxy. Thicken it with something like wood flour, which is basically a very fine saw dust. If you purchase filleting blend from WEST, it has 10% silica included, for smoothness, but that also increases the strength

I often used teak sawdust , just to match color, and add a tad of silica myself