We recently travelled with Ryanair over easter. We are a family of 4 and experienced a few frustrating issues in respect to seating. You have 2 options.
1) purchase designated seating to ensure you are sat together and are able to check in from 30 days before you Fly (Another expense)
2) Wait to be assigned seats by ryanair 7 days before you fly leaving you with the issue of sitting anywhere and apart on the plane and being unable to check in until 7 days before your flight. Well that seems fine going out, but means you cant check in for your return unless you locate an internet cafe. Our holiday villa is miles from anywhere. I did however notice that others were having a similar issue with this new 7 day policy and where using Checkinpal.com to take care of their online check in and boarding cards. Tried this option and it worked out saving us a fortune. added a link above which I thought may be helpful for anyone in a similar situation