My opinion is that you should not worry about it as your father is going pretty well.
I would suggest my patients the following things
1. Increase the intake of roughage and fibre .
2. Have more green leafy vegetables
3. Have half a lemon in warm water first thing every morning
4. Eat whole food direct from nature as much as possible
5. Eat several small meals throughout the day to prevent the sudden bowel contractions that large meals can cause.
6. Add a laxative and an antacid