Umm, to the OP, your baby is going to be 3 WEEKS old? Then you will definitely need a stroller that can accommodate an infant carrier. You cannot push a 3 week old around in a standard double stroller. Even the fancier ones are meant for babies at least 3 MONTHS old.
You will have to look into something that can take an infant seat. That removes the Peg Tender and I believe the Jane as well. The spider may be able to accommodate your baby, since it looks like it's well cushioned and can fully recline. However, even then, the seat angle doesn't seem okay for a 3 week old. They need FULL body support at that age, as you know.
I would perhaps look into the Combi Twin Savvy. It does accommodate a carseat, but I am not sure if it takes all brands or only just the Combi seats.
Otherwise, you might be much better off taking one of those carseat carrying frames and a separate umbrella stroller for your 2.5 year old. The Maclarens are very lightweight, easy to push, and there are several models which will provide the kind of support your toddler needs. Don't rule out two strollers. We have a 14 month old and a 3 year old and we go to
Disneyland about every 2 weeks. We have a Combi Twin Sport, but have found that it is actually easier to manage when DH and I each have one kid in a lightweight, easy to maneuver stroller. Plus, if one wants to nap, you don't have the other one RIGHT there yelling, kicking, or otherwise annoying the one who is trying to sleep, and you can fully cover the stroller with a blanket (we have to do this when they fall asleep or they will wake up too quickly) if you need to with two strollers. It's harder to do that with the doubles, especially the side by side models.