McQz,
Welcome back to the sport of cycling. I had a similar experience when I scaled way back on my riding about 25 years ago. There was an occasional short ride during the lengthy hiatus, mostly quick trips around town to pay bills and other errands. About one and a half years ago I decided to spend more time cycling again and have enjoyed it greatly.
When I first started up again in November 2007, a ride of 20 miles was enough to cause aches and pains. However, by slowly increasing the time and mileage on the bike, I was able to complete my first triple century last weekend at the age of 55.
It sounds like you have many worthwhile goals related to your riding, which should help keep you motivated. Follow the advice of the others here and take your time as you increase your distance, while being sure that you are each able to enjoy the time that is spent on the bike. Certainly finding a comfortable saddle will go a long way toward that goal!
Good luck and stay safe.
Rick