No idea legal-wise but...
Tunisia... there are certainly other places in a much more dangerous state sadly. In terms of probability of something bad happening then... the facts speak for themselves:
www.aon.com/terrorismmap/ www.aon.com/terrorismmap/Aon-TPV-Map-Cou...isk-Ratings-2015.pdf
Tunisia: "The overall score has been lowered from high to medium risk but the perils of terrorism and unrest remain the same. Since 2014, the interim government has begun to restore law and order to the country and combat the threat of terrorism, which worsened since the 2011 uprising. The threat is largely contained to Kasserine and Kef. Although political protests have dropped off in scale and intensity, often violent hardship unrest and strike activity continues to take place in the interior provinces."
So, I would share this with your ex so he can be better informed and hopefully it will encourage his vigilance.
I also hope sharing the above doesn''t worry you more but better to acknowledge actual truth than speculate instead I would suggest.
Albeit you share that your ex is being hostile about you attempting to intervene after the fact i.e. after the plans have been made it is a timely note to yourself to try and have better dialogue to avoid that happening again and be ready to raise the discussion ahead of your ex acting in isolation and thus ensuring you are being consulted through your own pro-active pursuit of discussing future plans.
If you still feel this (risk) is not at all something you want your children to be exposed to then rather than contest this directly with your ex, as you have tried, it would be best to seek legal advice to help you do so as the hostility is a firm barrier to your attempt to do so and it would be pointless to continue attempting to do so on your own I suspect though do at least share the information above, as a last chance attempt to better inform them ahead of you seeking legal action to prevent this if that is your wish.
Finally, it is very much Tunisia''s intention to protect a valuable part of their economy (Tourism) so one can expect their efforts to be of merit:
www.euronews.com/2015/06/03/tunisian-pri...orism-is-a-priority/
...that said the cruel aspect of terrorism where ever it occurs is that it is very hard to prevent:
www.washingtonpost.com/blogs/monkey-cage...ecurity-and-freedom/