You can do that 67 miles. I just bought a road bike on July 2nd, after a 25 year lay off from cycling. I am 54 years old and I started a pretty good training progarm on July 4th. I am now up to 60 miles. Did a 60 mile mostly flat ride on Sat. and I am doing 60 miles this Sat. but with more hills. I am training for my 1st Century in Oct.
There has been a lot of good advice given here. Just remember to drink plenty of water and electrolytes. You will also need to eat for energy. Do not wait until you are thirsty or hungry, start drinking and eating 15 to 30 minutes into your ride.
Good luck with you training.