WE only went once, after many trips to WDW. We did TL, so I can't comment on one vs. the other.
It was fair amount of waiting in line. If the youngest is too young for many slides, and you only have two adults, that might end up being a not-so-exciting day, where one adult has to tend the toddler while everyone else is in line/riding. Depends a little how tall youngest is, and how brave around water (swimming?) Might make sense to wait a year or two until youngest is confident around water.
We were warned that on busy days all seats are gone by mid morning. I think we arrived about 10am, and had to search for a seat. By mid afternoon though some guests leave. Also watch weather for afternoon thunder- common in summer. May want to allow options in your planning to swap days in case of weather issues.
Think ahead about what to bring and what to avoid bringing. We drove, but then had to find an idea to hide our keys. A small water proof pouch is good idea, and not bringing any kind of purse. Anything left in car gets HOT!