Not a running expert but I have trained with an Ex-Pro triath guy. What's your idea of "sprinting"....I wouldnt waste time in 100yard running as it's not what you are training for. I would look more at 400-800m repeats (1-2 track laps) on your short days. Build up the quantity each week. Then do a longer day which may consist of mile repeats. It's only a 5k....I really don't think you need to run that distance to get used to it more than 2-3x over 12 weeks. I'd keep your training schedule flexible to judge recovery and times. Get a good stopwatch to wear and time all laps. If you are not seeing improvements weekly then you may be overdoing it. Like I said, not a pro but I would go with something like this (and it will depend on your base right now for volume)
Sprint Day (1x/wk) - warmup 800, timed 400x3-4 with 2:1 rest ratio (if you run for 1:30, rest for 3)
Longer Day (1x/wk) - warmup 800, timed milex2-3 with 1:1 rest ratio (personally I don't like tracks, so I have a 1.5 trail run I do repeats on and time every lap)
then as the weeks progress either add 1-2 800s into your sprint day, add more repeats, lower the rest ratio, etc..etc..etc. Really you should see all times going down and down.
If you want a base value for 5k, run it week 1, 4, 8, 12 on your long day....to see times. You will start knowing what your sustainable race pace should be.
Hope it helps....this coming from a hockey player....who hates running...and loves beer....