Firstly, assuming there are no specific arrangements in any court-authorised divorce agreement regarding the mother's right to take the children abroad on holiday, then the general principle applies that the children cannot leave Israel to travel without the consent of both parents.
In other words, a parent , as a biological parent and a natural guardian, has the the right under Israeli law to prevent his/her children leaving Israel, though this veto can be overriden by court . Removing the children from Israel , the country of their habitual residence, without your consent would, prima facie, be an act of child abduction, according to the 1980 Hague Convention on the Civil Aspects of Child Abduction, even if your 'ex' is the custodial parent. The status of custodian gives her no right to make unilateral decisions about the children travelling overseas - she still needs your consent.
If you refuse to let the children travel, then the family court can rule on the dispute. Your ex would have to apply for and obtain court permission to take the children on holiday, to make their departure legal. The court would have discretion about allowing or refusing their trip. Your opposition could be overriden, by court order, if this was considered to be in their best interests, subject , if necessary, to suitable financial guarantees of the minors' return.
You could initiate legal action for an order to prevent their exit from Israel, based on reasoned and reasonable opposition, especially if there is a risk that she will not return them. You would be advised to see specialist legal advice on this. In emergencies, temporary ex-parte orders are granted, but afterwards a hearing is usually set before both parties.
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