I think it really depends on the atmosphere you set for the wedding. If you make it a formal invitation kind of thing, then I would think you should pay for dinner for people. However, if it's more of a "if you want to come, come. We'd love to have you" but you make it clear that guests are expected to pay for their meals, then it's their choice to come and just be a part of your day or not.
I went to a destination wedding in Maui once of a granddaughter of a friend of my mom's (my mom used it as an excuse for a vacation

). It was a very small ceremony in a garden. I think only attendants, parents, and grandparents were there. The bride and groom said they were going to a Luau after the ceremony, but we were aware we were to pay our own way if we wanted to join them. We went, and it was fine. It was our choice to go or not. At first I was a little surprised since there weren't many people there and I was used to the bride/groom paying for a "reception," but looking back on it, I can see why they did it. It wasn't a big or traditional wedding, the travel expense was a lot as it is, and the guests knew what was expected.
Now I was not a family member of the wedding party, so I wasn't really attached to this wedding, and the whole point for me to be there was a vacation. So none of that bothered me. But I think it really depends on if the guests understand the expectations up front. If they choose to go knowing they have to pay, then they obviously don't mind. But for others it might be a deal breaker based upon finances and travel distance.
Oh, and I would NOT expect the bride/groom to pay for tickets for me to the parks especially since park tickets are not required even for ceremonies in the parks. The main purpose is your wedding; it is the guests' choice if they want to go to the parks on their own. HOWEVER, I would not, then organize a group event of a day in the parks or eating at a specific park restaurant that DOES require park tickets in case your guests are not planning on getting tickets. That would put them in a position of either not going and feeling left out or being forced to buy tickets they didn't intend (and maybe not budget) to buy.
Good luck!