I think the problem may be a lightweight stroller that holds 50 pounds. I know my maclaren will (even though I think it says up to 40) but I doubt you want to spend $200 on a throwaway stroller. I don't know how much weight a typical umbrella stroller holds, but that is worth checking into.
There are lots of stroller threads floating around, if you search, but I think you'll have to go to the store & try some out.
I really love my maclaren, but we took a century stroller to disney (similar to many of the gracos) and loved the convenience of having a nice basket & 3 cup holders. It looks like a slightly larger version of the Graco Kite Lite, which is nice WDW stroller, at least for smaller babies. If the kite lite can hold your child, I'd look into that.