Hi Gerry,
I would say that as long as you re-inforce that Rigsby is top dog in the house hold (treats / dinner / fuss first) that Dylan will soon learn his place in the pack.
Have you met him yet? As if not it might be a good idea for you and your family to meet Dylan first and see how you get on with him.
As he is a bit older than your average pup, I would say perhaps a meeting on neutral ground might be best, then you can take them for a walk together.
Cockers are generally very sociable friendly dogs who just love other dogs, so providing neither of them has a dominance issue then they should love each others company.
I sure the others will be aong later with more advice, these are just my ideas
HTH
Kel