He's adorable, I love birds at this age.
I need to be honest here though, if you're not confident with rehabilitating wild animals, I don't recommend it. Firstly there's correct nutrition, which is going to take a lot more than a basis of crickets. But nutrition isn't even the biggest obstacle in preparing an animal for life in the wild. If you raise him up on handfeedings and snuggles (who wouldn't want to, right?), and then you release him, sadly there's a very good chance this little fella will die.
Don't get me wrong, if you saved this little critter from a dangerous situation, then you've done a great thing and I would hug you for it. At this point I would personally hand over the rehabilitation process to a wildlife professional.
I recently talked a friend through administering first aid care for a malnourished, dehydrated magpie fledgling that had become temporarily blind due to the lack of proper nutrition (a different cause, the avian vet believes that neighbourhood people have been feeding the magpies substandard food, which they then bring to their babies leading to malnutrition). It goes to show how easy it is for people to make mistakes when they believe they're helping an animal.
This magpie has since been taken to a wildlife sanctuary for rehabilitation, and when it's ready to be released, the guy that rescued the bird will get to go along for the release. It's a really satisfying experience, and if you're keen to be a part of it, I think that's the best path to take.
If I were you, I'd make some calls around to some local wildlife sanctuaries and/or local avian vets for advice. When you find someone that's able to care for the bird and prepare it for release, just ask them if they'd let you be a part of that. Generally the people I've struck at those places are lovely caring people, and if you show them your passion for these animals, there's a good chance they'll be more than happy.
All the best. Keep us updated, yeah?
Renae
EDIT - I forgot to mention. Yes, in the meantime you'll want to keep the bird at a steady temperature, slightly on the warm side. Don't overheat the little fella. Place the bird in a box with a bunched up towel (makeshift nest). A low wattage heat mat under part of the box will do just fine to keep the temperature stable, just ensure that the box is raised slightly to allow air to circulate over the mat.
You're going to need to move pretty fast to find a suitable carer. I'd start making calls first chance you get tomorrow. I'm happy to PM you or even talk over Skype if you need any help getting some fluids into the little guy (safely, please don't attempt anything that could lead to asphyxiation.)