Combi Savvy. Very lightweight. Folds easily. It only has a 37 lb weight limit but my 48 lber sat in it today and it still rolled very easily. It does have quite a narrow seat, though. .
We have this as part of our 3 stroller garage...
The thing is lightweight enough.. easy to carry.. negatives is the storage is a paing to get to. They have the wheel mounts blocking some usable space on it. Also, it can be a pain to turn it. And the cover doesn't fold down far enough if you have sun facing you. It also doesn't recline fully.
We have our Graco "bertha" unit that is part of a travel system (we bought them seperate though to get the color we wanted). Our DD4 still uses this one at times if we go somewhere with just her for a long period of time. The storage on this is great, easy to manuever and the cover folds down to block the front. Very nice...
We also (not yet for you) a sit n stand unit. If we go a day trip we will use this one for our DS1 and DD. Storage is ok, but usable.
the last time we went to Disney, DS was 8mo and DD was still 4. We actually took both single strollers.. DD got the Combi with me pushing it and the DS got the graco. When DD wanted to walk, I folded it up, and slung it over the handles of the Graco. This way we could split up as needed.
I would say the most important thing for you are these two points..
1) get a stroller that FULLY RECLINES.. goot for changing diapers and for sleeping. especially a 5mo.
2) get one with sufficient cargo space.. if you look at the Combi (
http://www.combistrollers.com/ProductImages/large/helio_carbon.jpg) look at the rear leg support where it cuts across to the storage area.. this pic has a bar running across, but ours doesnt but it has semi bars. This particular model is a pain to stick larger items in there..