Okay, the general things are...
Mineralised bones are stronger, but also heavier. Honeycombed bones are stronger and lighter, and can be cannibalised from birds. And again, a hollow bone isn't a weak bone. A peregrine, with its little hollow leg bones, can still withstand hitting a pigeon in the skull at ridiculous speeds. If it's that much of a problem, however, we can always manually thicken the walls so it's more like a mammal bone with a honeycomb structure, since our bones have marrow-filled hollows in them anyway.
A bald head has no protection from the sun. A hairy or feathered head does have protection. Feathers are better at losing heat than hair, so feathers are the all-round superior option.
Complete cold-bloodedness won't give them the energy to have human-level intelligence. I'd recommend a simple lower body temperature, instead of going all the way. Platypus have a lower body temperature than normal mammals, but are still warm-blooded. Even more warm blood would mean they'd have to eat more food, which doesn't really help a colonisation attempt.
Sails generally don't work with warm-blooded animals, which our humans will need to be if they're intelligent enough to be people. They make blood overheat in the sun and you end up burning more food to stay warm if it's against the wind. It would probably be cheaper not to have to make custom clothes, too.
Downscaling is a good idea. Less food, can use smaller shade, and won't take as much damage from a fall.
The urea+digestive system idea is a good idea, although I'd still prefer uric acid.
The plants would, most likely, give a neglible amount of oxygen and sugar. It would be far easier to use a traditional hairstyle of some sort, and you wouldn't have to grow the seeds on your baby's head.
The binary heart isn't really necessary, it just needs to be a reasonable size.
I'm all for making Velociraptors, but that isn't really part of the task we've been given. Perhaps later.