I don't think it would be right for Luffy to fight Shanks. It would feel sort of out of place imo. I have a feeling that Luffy will meet Shanks somewhere close to the middle of the end. Shanks then notices that his hat has been safe and in good condition and maybe, just maybe, they have a light spar match to see how strong each other is to test their own powers, specifically Luffy. Pretty much a battle to see where each others strengths lies.
Of course Shanks will win, but Shanks will be amazed out how much stronger Luffy has gotten since he last saw him. After all that good stuff happens, they will part ways and set out.
When it comes to Shanks, I feel he is just testing Luffy to see if he has what it takes to become the strongest Pirate. Shanks is not even an enemy of Luffy. I feel that other people will get in the way of Shanks and kill him. This will cause uprising in Luffy and give him a reason to go even further. Shanks will probably die to someone of superior power(Blackbeard) and Luffy avenges his death and faces off against him.
When it comes to Dragon, that meeting will be more emotional on Luffy's part, but then again I expect Luffy to act like he normally does and be goofy and not show signs of caring. Luffy showed signs of care for Sabo because he thought he was dead and they actually became close. I wouldn't be surprised if Luffy didn't show and concern or care for his father seeing as how he never even met him.
When they meet, I expect a more forced battle through the heart explaining why Dragon was not there for his son and many questions that need to be answered like why he is the major threat to the marines world government.
As for your question, I am more excited with his meeting with Shanks. I want to see why Shanks is so strong and what he is capable of. I also want to see the interactions between them. Maybe Luffy will cry after not seeing him for so long. He cares so much for that hat that seeing the one person who actually gave it to him would be even more heart whelming.