Would you attend a wedding under these circumstances?

It totally depends on the individual circumstances. On the plus side, they're not new parents, so they will have experience of life with a baby - but having two is very different to having one, and many people with one child who confidently expect to be able to carry on the same way with two find they're not able to.

Also, so much depends on how the pregnancy and delivery progresses.

In your place, I would let them know that you would love to see them, but also that you understand totally if they don't feel able to make it. If the baby is due 6 months before the wedding, then hopefully they should be able to see how they go through the first couple of months before making a decision and still meet your RSVP deadline.

We had friends at our wedding with their 4-5 month old baby and he was less work than the toddlers of other guests.

So I wouldn't expect it to definitely be a no just because of the baby's age. Although your guests have the addition of international travel so it depends how comfortable they are flying with children.
Do you have accommodation on site that they can use? If so then they can split themselves between the party and their bedroom when the children are ready for bed and then switch so they both get to enjoy the night.