Hi, Kim!
You will be pleasantly surprised to discover the numerous attractions you can experience with your infant. Any attraction that does not have a height requirement you are able to ride together - this does include Kilimanjaro Safaris. The Disney Parks Blog has an easy chart that can help you see Walt Disney World Resort attraction height requirements sorted by Theme Park.
A Sit N Stand stroller is a fantastic idea. We used one when my boys were 1 and 4-years-old. It was a great way for my older son to be able to rest for a bit without sitting in a stroller - he was a big kid, after all! When visiting the Theme Parks, be sure to leave your stroller in designated stroller parking areas. Strollers are not allowed in ride ques. It may be a good idea to attach something to your stroller so you can easily locate it. At times, Cast Members may need to move your stroller a bit so it may not be exactly where you left it. If you are using Disney bus transportation, you need to fold the stroller before boarding and keep it with you while riding.
Each Theme Park has Baby Care Centers where you can comfortably attend to all of baby's needs. Here you can find private nursing rooms, high chairs, full sized changing tables, and even a TV and comfy chairs to allow older kids to sit and rest for a bit.
Please visit us again if you need any additional planning help. Have a magical day, Kim!
~Rachel