Look at the streaming options (in System Preferences APP/iCloud)
But if you are elderly and can wait a moment, there is a new "Photos" app coming out - probably - with the next Yosemite update. Some things may change with this and waiting would avoid you learning everything twice.
I'd wait until the Photos app comes out for Mac on Yosemite*. Then you can import your iPhoto library into the Photos app and upload them to iCloud Photo Library. Then you can choose to have the full size photos on your iPhone or have smaller ones and just download the full ones as you need them. All of your photos will be synced across your devices.
*If you're not running Yosemite, then you will not have access to the Photos app on a Mac. Your photos will be in the cloud, but I don't believe syncing with iPhoto is as seamless as Photos.
As others have said - Apple is going to bring out a new program (called "Photos") to replace iPhoto in the next month or so. So maybe wait until that's here. As it is going to be much better/ easier integrated with iCloud.