I want to take kids to New Zealand to visit my new husbands relatives We have been 2 times since marriage and never taken the two eldest children as the Ex husband has refused to allow us to. We want to go for 4 weeks. We just had a baby and want to show him off to my husbands family in New Zealand also its the inlaws ruby anniversary and the grand mothers 98th birthday plus my new husbands parents are getting older and there is farm and future issues to discuss BUT the ex husband wants a guarantee that ill bring back the two children we had in our previous marraige together. I have no issue with this what so ever, i totally understand why he may even want one and thats fine but What can i use as a guarantee is the question as words arnt enough i don't think.
When i asked him what would be a guarantee he said i don't know. Yet thats the only reason thats stopping him from saying yes to getting the passports. Any ideas. Obviously the fact i am renting and have a house load full of things and all my family is in Australia doesn't help him feel any more assured. Let alone i have a caravan and car too here.
Help any ideas?

I already suggested phone call and internet and web cam dates and times. I said he could have every contact detail of our locations over there and even ring the inlaws to confirm what we are doing and where we will be staying.
I said ild give him all my bank details even car redgo number of what ill be driving over there. I also said ild give him the red book from birth for all kids. And as any mother knows this book is essential for daycares and schools.

HELP WE DO NEED MORE SUGGESTIONS and ideas?????