There are really a lot of great carriers out there for toddlers!
For heavier kids I prefer ring slings for quick up and downs and wraps or a structured carrier for periods where the child will be carried longer. I like the Ergo for a structured carrier. I also like the Patapum, but slightly prefer the Ergo to the Patapum (because I have an easier time getting the Ergo on by myself). Wraps are awesome, but can have a higher learning curve and can be a on the warm side. We used to live in Florida and I can tell you from experience any carrier is hot because of the body heat issues, extra fabric, etc...Solarveil and solarweave are available in some carriers (ring slings and mei tais), and they are wonderful and very breatheable fabrics for when it it REALLY hot, but I probably wouldn't use a solarveil or solarweave carrier as my main carrier because I would worry about pressure points with long carries and I would worry about how it would hold up with very, very frequent wear. My suggestion for a good long term carrier for a toddler would be an Ergo or a Wrap.
Maybe some other mamas can chime in with suggestions 