Although the one cone is in bad shape, both of those will play nicely after repair. Your choice of conservation adhesive sounds like a good idea. As was posted, you can double layer the tissue paper or use thicker stock but it probably won't be necesary to add a lot of strength to the damaged area. If the adhesive is good, it does most of the holding. I've repaired much greater cone damage and had good success.

Good luck on your speaker build!