I would encourage you to chip the pups. When you travel it's a big relief to know they will be safe if something happens. I had all three of mine done at the vet during their routine visit. There was just one little wimper, no more than a vaccination.
We have had our kids watch the pups for a week and I knew if they scooted away I would get them back.
Yorkies are so curious and fast. I don't let mine out of my sight ever......Things happen, though.
If they run away, it may take awhile to find them, but at sometime they would be taken to a vet. If the vet determines that the person bringing them in for care isn't the name on the chip, they will not let the person have the dog back until they prove they are the owners.
My vet was able to get a yorkie to it's proper owner. The thief had dyed the yorkies hair and changed the style. The thief lived in our town. The thief was very mad and indignant at the vet for not trusting her.
When the Vet called the real owner listed on the chip they said the Yorkie had been stolen right out of their yard while out for a potty break.
The lady was their neighbor and they did press charges and the lady was convicted.