My mom thinks I'm abusing my child!!

My husband and I takes my 11 month old son to a near by lake which has a beach and place to swim and have birthday parties but anyway even though we put sunblock on my son from head to toe. my mom and grandma thinks I'm abusing him. My dad told me that it wont be the last time he gets sunburned. we didn't take a canopy because we didn't know if they were allow like they are in Florida so that's one reason we didn't one. I don't know what to do about this situation...any suggestions?