You really only have a few options. One is a nursing home or also called a long term care facility. Depending on finances and the state you live in can be one answer to care for your dad. The LTCF will assist with all daily living activties and continue all medications your dad may be on. I would check with your state's board of health for the scores and reports on any LTCF you decided on.
Second, is hire someone or go through an agency to find a caretaker which can assist your dad for part of the day. This too depends on what state you are living in and what assistance he may quailfy for. The cost as compared to a LTCF is somewhat lower, but a 24 hour care can be astronomical. Not to mention if you have to search without an agency you are going to have to research the person's background on your own.
Third, you might check with the church which your parents attend. You would be surprised how many are there to lend a helping hand with caring for your dad.
Fourth, if your dad and mom have decided to no longer treat agressively the giolblastoma then there is hospice. Hospice will provide a Certified nursing assistant to come in and help assist with bathing, dressing, bed making etc. They also will provided all durable medical equipment, medication and nursing related to his diagnose. By choosing hospice this does not mean you have given up, but means he can stay in a loving home with close supervision of his illness. He can continue to seek medical treatment for other aliments which he may suffer from. The only time he will need the consent for treatment is for the Hospice Diagnose. Should your dad get into a crisis there is Continous Care which is evaluated every 24 hours by the registered nurse. There is also bi-weekly team meetings which discuss the patient and his continuing on hospice. The family is not forgotten in hospice. When there are minor children involved social work and breavement to help prepared the children for a death. Spiritual support is another aspect of hospice which helps address issues of the spirit for both patient and family. Respite care is also included in hospice which gives the caregiver a break and time to regroup. The volunteers are an important part of the team because the majority of them have been through the same thing you are going through now. Hospice is there to support not replace the caregiver. I would address this with mother first and then with dad. Remember you can call any hospice and they will assist you. You do not need a doctor's referral to enter hospice.