Yes, if overnight travel more than 50 miles from home, must provide physical address and phone number for location to the non-traveling parent.
Like so much in these situations, having the written legal right to something is far different from having something.
Get your children a cell phone. My boys have a prepaid cell, no data plan. Flat rate per minute and per text. Don't make a big deal about the cell with stbx. Try not to react when he removes the battery, takes it from the kids, and claims you are trying to "control him." (um, yeah, that happened.)
As for the super secret pie in the sky vacations... It sounds like fantasy.
Definitely address the secret keeping thing again with the kids. My kids shared plans to go to Disney World, to fly to some far away state to visit OW's family and I overheard ex promise to take DS fishing in...... Mongolia! yep. Plans are just talk. Lack of overnight visitation? Big stumbling block dude.
eta: the kids have not taken those trips, big surprise. Car trips have been taken and ex has followed the decree about 50% of the time, or only provided half information.