So my dad wants to rent an Suv to go to my bros graduation and he has Allstate Insurance and its full coverage what ever that means well anyways how do we know if it covers rental cars or does it cover rental cars?

Generally yes. As far as I know you have to have insurance before you can rent a car, or you have to buy it through the rental company, and that can cost a fortune.

call and ask or check the policy for what is covered

It depends on the policy you hold with allstate. But remember that if anything happens to the SUV you rent, your insurance will end up going up.

When you rent from a car rental compny they offer you insurance, for like $9 a day you can cover the vehicle bumper to bumper with no deductible, and you dont have to contact your insurance if nothing happens. thats the best bet.

I used to work for 2 car rental companys, and it really is easier just to get the insurance through the comapny like that.