Is this an Irrational Request?

My parents want to take my 15 month old out on the lake this weekend, just the two of them. I asked them to bring my brother who is CPR certified, and if that wasn't an option, to watch some tutorials so that they would be educated to perform it if necessary. They told me I obviously don't trust them and that was a ridiculous request. Then they refused to do it. Am I being irrational? My husband, myself, and all of our babysitters know CPR and theHeimlich.