Hi Andrea -- Simpson is a very common surname and you didn't include any dates, or approximate dates, for anyone in your query.If you don't have any dates on Edgar or Margaret, how about birth date for any of their children?
This looks like a possible match, but without dates of any kind I'm not sure.And, first name is Delbert, not Delber as you gave.
Combined info from TX Dth IdX and SSDI:
Simpson, Delbert Raymond, b 17 Mar 1917; d 12 Nov 1968 Tarrant Co, TX; no last residence shown;SS card issued in OK.
McDade is in Bastrop Co, TX.Here is a handy dandy site to locate county for TX towns/cities.