Hi Chris and welcome;

Just my thoughts;
1. 14mm, I have the 24mm, 35mm and the 16-35. I never use the 16-35 anymore and have often thought of getting the 14mm. The 14mm is super wide and would be fun, but it really is a specialty lens.
2. 200mm 2.0L, if you shoot indoor sports it would be a good addition. But you have a 70-200mm II f/2.8 so I think you could benefit more by a different focal length.
3. Lots of uses for the 300 F2.8II. Even with the old version of this lens you could put a 1.4x on it and almost see very little loss in IQ. I own the old version, for the daughters softball games it is almost to long and I end up using my 70-200mm II sometimes. For the grandsons baseball games it is perfect. For the sons graduation in an indoor arena it is perfect. For Zoo trips it is perfect. For wildlife it is on the short side but with the tele convertors it can be adequate. The supertele's are big lenses, this one you can hand hold, but for me it isn't to much worse than carrying the 70-200mm II. The IQ is a very noticeable step up from the other lenses you own.
4. 400mm F/2.8 Forget this one unless you shoot pro sports. I have never seen a situation that I thought I would like to be carrying that thing around. There are better lenses for wildlife. Go with a 500mm II or a 600mm II for wildlife, more reach and IQ second to none. I have been to races, kids ball games, pro games and many other events in the last few years. Most pro events wouldn't allow a fan to carry it in. It would have been to long for the kids games.

Good Luck
Rick