Dryer Outlet Splitter - Buy or Make? 10-30
Let's start with the fact that the 10-30R is an obsolete receptacle that only exists because the NEC 250.140 says it can if it is existing   (the grandfather clause). To try and use for any other appliance or machine would violate the NEC. The cord and plug splitter is an attempt at an end-run around the NEC but since the equipment isn't existing then you cannot use the neutral as a ground. You really need a plug and cord with a NEMA 6-30 configuration on any equipment whose voltage rating is 240V with a ground and no neutral.

Also NEC 210.21(B)(2) says you cannot connect multiple cord and plug loads totaling more that 24A on any 30A circuit. I can almost guarantee that your dryer pulls 4500W which is 18.75A so your saw, jointer, whatever can only pull 5.25A or a 1/2 or less HP motor. The fact that you say "I am not going to use them at the same time" doesn't really apply in the NEC.

Conclusion You cannot use your neutral as a ground on any equipment other than your dryer without an up grade of that circuit, and your loads are probably in violation of the NEC.

Best advice - Tell your father that you and your wife are moving in with him until the new circuits are installed. I know that would get me down to my sons house the next day. 

Hope this helps.