I love my Mockingbird stroller and they have a dual seater stroller for newborn and an older infant/toddler. Different attachments too and it's cheaper than the Nuna but is very comparable. I also like that it's not too heavy as well.
Definitely Bob stroller
Uppababy Vista
My kids have about the same age difference.. I had the Mockingbird double for a while. It gets heavy pushing 2 around and my oldest started wanting to walk more so I hardly used it. I think it'd be better to get a wagon or use a baby carrier depending on what kind of activities you're planning to use it for
Hi, I recently switched to Cybex gazelle s2 and I love it, perfect for 2 under 2 I used to have nuna demi next and was super heavy and it was a pain to carry the extra seat