You may re-release the TBs, once you're certain they're gone. They can turn up again someday. But certainly at 12 months with no word, you could make a revived TB.
And you don't have to drop the new TBs into cache containers. You have some options.
You could bring the TBs with you, and log Visits on caches you find. You could have a whole set of TB numbers on your car for people to discover and for you to log Visits.
Or you could make "trackable" shirts or hats or stickers for the kids, so they can have the TB number.
When I revive mine, they are always a major upgrade, a much nicer version of its theme. Way too cool to put it into a cache, so I keep them. One I use for Visits to caches, now has a solid silver claw pendant, so of course it stays with me.
Oh I like those ideas. I have two trackables MIA right now - will start working on a proxy to be released at their one year anniversary. If the originals do show up and become active once again...? Well it will be an awesome sight!