I too have seen this triple decker stroller that was mentioned, but I don't
think it would be of use to a family with a toddler and two infants. I thought
I remember it to be a frame that holds the infant seats, but not having a
regular seat for an older child. Don't quote me on that!

I do NOT recommend the stroller connectors that you mentioned. They are
supposed to be used to connect two umbrella strollers but they do not function
well at all with two strollers I doubt it would be any better with three.

My suggestion is something like the Graco Duo Glider that accommodates two
infant seats and then can be used for two children after they have outgrown the
infant seats. They could then attach one of those sit and stand things to the
back of the stroller so the older child could sit or stand on that.

They could also use the duo glider and a snap and go when they have an extra
pair of hands around. They could put the older child and one of the babies in
the duo glider and pop the other infant into the snap and go.

I had two snap and go strollers when my twins were infants and DH and I would
each push one baby around when we were together (they did not have the double
one when mine were born). I also had the duo glider when I was alone with
them, which was quite often. The infant seats pop in and out very easily and
it helps a lot to not have to disturb a sleeping baby when transferring from
stroller to car.

Good luck to your son and daughter-in-law. I am sure they appreciate your
help!

Michelle
Mommy to Riley Claire & James Michael
http://www.babiesonline.com/babies/r/rileyandjames/