Yo Jasper,
Here's the deal mang... it all depends on your aim. If you aspire to get a serious turn-out, you might have to take the political approach and rub some elbows. But, from my observations, if that is not done correctly, you might be truly disappointed.
However, if you are truly just interested in putting on a tourney, build it and they will eventually come. Even if you pick a date during or close to another established tourney, that might be o-kay too.
First and foremost, see what type of local support you might have and go from there. Secondly, try to pick a time where most local folk will be available and will not have plans to attend another tourney.
Once you've done that, build it and eventually more might partake. Try not to concern yourself with too many other things for coaches outside of your locale. The reason I say this is because you simply can't depend on them. Create your foundation locally then advertise, but do not expect a huge helping of support from outside coaches. If you get that... great, but do not base your tourney on it.
Once you have established it and hyped it, more and more coaches will become interested
and might actually test the waters. Do yo thang mang... do yo thang....
Peace