I do not stop at rest stations except for water until I get to around 65 miles. Then it is eat something more substantial -drink a full bottle- stretch a bit and go.

But on these organised rides there is always some one or a group going at your pace. Just don't get on a group that makes you breath hard and overextend yourself and don't stay with a group that is just a bit too slow.

And as the milage is longer than you have done before and it is a bit hillier- put a cassette on with a lower gear than you would normally run. You may not need it- but it could be tough if you do and it isn't there.

Normal rules apply of drink- eat and take pics.