Good to see you have gone to so much trouble to read up about your fish now Goldigirl. You are right, goldfish are adaptable but that doesn't always mean they are happy!
They will accept quite a temperature range but the warmer the temperature I am told, the shorter their lives will be. It sounds like you have them at a good temperature now (I am so pleased I have a calculator which converts F to C degrees).
Are you able to read pdf files on your computer? You need a programme called Adobe Acrobat Reader. If so, I would be happy to add you to my email list of non club members who receive a monthly copy of Fishtales, the newsletter of my local group, the Marlborough Aquarium Club. Newsletters can be up to 850k when there are photos added. One of our members actually lives in Venus, Texas.
Happy fishkeeping...