If you find them - remove them right away before they have a chance to
develop.

The sparse material I've read about apple snail life cycle says that
the snails should take about 2 weeks to hatch. Based on when we got
the two snails and when the first egg sac hatched, that seems about
right.

So, as long as we check every couple of days, it sounds like we'll be
OK...

I like the idea of taking the eggs out manually anyway. I have to
imagine it's less stressful on the female when she can actually lay
the eggs (rather than absorbing them or laying them in the water).

This next part was very helpful:

You have the stomach for live feeding (you're feeding your puffers
with pond snails), so I'll tell you what somebody said they did with
snails on another group.
They feed birds in their yard. In a shallow dish, they placed a little
water and the snails. They didn't last long.
I have never done this before.
I feed seed. = )

I wish I had read this yesterday -- that's a fantastic idea.

Yesterday, we removed three egg sacs. We put them into a ziplock bag
and smashed them. Luckily, they smashed easily, but we felt pretty bad
about it nonetheless. It's one thing to feed snails to something else.
It's quite another thing to destroy them for no decent reason.

That being said, we really worry about these snails getting out in the
wild. We live by a "lake" (an old rock quarry), and we don't want
these things to have the chance of invading. I suppose as long as we
put these things outside when they're very young, the birds should
digest them easily before they could possibly cause a problem. We
already have a few feeders, so a bowl full of snail eggs will fit
right in.

Thanks for the help!

--Ted