You might want to buy an all weather box, some 4 ga wire, another 50A double pole breaker and a new 50a plug and just wire in a new 50A outlet and hang it on the same pole. I live out in the country and do this type stuff myself but if you are more comfy with an electrician doing this stuff, can't imagine it would cost a ton of money. I don't think a Y from a single 50A outlet seems to be a good idea but I am not a pro.
http://crushtheroad.com/how-to-wire-a-50-amp-rv-plug/