Okay, I have the valco double with toddler seat also, LOVE IT!!!! I actually sold my beloved Mac Twin Traveller, because it just never got used anymore! So, I've just got the Valco and the Infinity now.
When I was a nanny, the family had a double peg. That was the worst thing to push!! I couldn't imagine pushing the triple! If you were on any incline/hill at all, it was just the worst. At the zoo it nearly tipped over with the girls in it! After that incident, I never used it again.
I wouldn't recommend the Baby Jogger, unless they are never going inside anywhere. IIRC, that has the seats 3 across.
My votes are for the Valco double with toddler seat or ABC twin (if available in Canada).
Any cheaper choices they have nixed because they won't sling a baby or use 2 strollers. The could have done the peg 60/40 with a baby and 2yo, push the other baby in their current stroller and still use the infant seats.