Hey vk. Welcome to the site.
As ST2 mentioned, Sentinel cave is well below the chain ladder, and thus not a far walk from the car park in fair weather. However, even recently, some have fallen foul of the inclement weather around this area. Do not take it lightly, and rather pack at least one tent in case, even if you do not plan to use it. I have not as yet been to Crows nest, but the security issues around Tugela Falls are of concern. The access is really easy for would be thieves, and they are accustomed to the area, far more so than any of us. However, on the flip side, many others have tented around the area without issue, but I would advise against tenting there without at least being aware of the issues. If you are aware of the issues and have taken consideration (such as pepper spray/mace, a bright torch that can blind would be thieves, and sleep on your kit in your tent) of the issues and taken precautions, it is my experience that this planning is generally unnecessary. Call it Murphy's law if you will, but to date I have yet to have run ins with thieves, because Intrepid and I have been cautious and known about the security issues and prepared for them.
It is a really stunning piece of the landscape of this country that I plan to go to very soon again, but with the correct mindset and preparation, it will be better for the all-round experience.
Let us know how it is up there, for those who are not as fortunate to get out there as often as we may want to!