You probably aren't going to get the 70 photos compressed in an acceptable way to fit within the 10 MB limit.
In iPhoto you have 2 options, depending on whether or not you have Mail configured.
The easiest is to select a batch of photos, then click the "Email" button in the bottom right. Versions will be automatically compressed and attached to a new message in Mail.
If you're not using Mail, select your photos then choose File -> Export. Size and quality sliders to choose how much reduction/compression so you can play around to hit the 10MB limit.
FYI, the same export works for getting pics prepped for WW. Export, then choose a custom size (I use 800 pix).