I have a running dilemma. Anyone care to give me some input?

Here's the background:

I am running 5km 3 times a week now. I can run M and W, or T and Th, and then a longer run on Saturday. I also bike 3-4X a week and swim 3X a week so getting all the workouts scheduled and done takes some planning.

Further to that, I've been struggling with shin splints for the past few months and I seem to be able to run thru it because they simply aren't hurting when I run so I think that's ok. However, I don't think I can run two days in a row or I'll get in trouble and I have been following the 10% rule very strictly.

So that's the background, here's the problem. My school has a noon-hour running club starting next week for about 5 weeks. I really like to be a part of it because 1/3 of my students are involved and to a big part, it's because I'm there. We run at noon. It's 2km for a few weeks, then we bump up to 3km. We run on T and Th. I'm trying to figure out how (and even if) adding this on will impact on my training (I suspect it will).

My choices are:

1. Do my regular 5km runs on M, W and then run with the kids 2-3k on T and Th. (I worry about my shins running every day.)

2. Run 2-3 km at noon with the kids on T and Th and do the rest of my 5km after school. (What happens to my endurance is I split my run up into two parts during the day??)

3. Run the whole 5km at noon on T, Th - 2-3k with the kids, and the other 2-3 k alone. This is a bit problematic because we rarely start right at bell-time and I may not have time to finish my 5km before I have to go back to class (I may not have time to eat either). I MIGHT be able to leave right away, do 1km alone, then meet the kids and run another 2km, and then finish up on my own but it'll still be a bit tight. (There's also the sweat factor. We have no showers at school so I'll be yucky for the rest of the day. I can live with this though...)

4. Some other idea?

Thanks for your input.