Hi M.,
I have never been to the "ocean" or "the beach" but, 1 of my favorite places to go is the Henry Doorly Zoo in Omaha, Nebraska. It is an awesome zoo, they have the rainforest there, an aquarium that is realy awesome the cat house, and monkey house all of these things are inside so even if its a little chilly or hot outside you can go indoors and cool off or warm up.
The rainforest you go in at the top and as you go threw it you slowly get to the bottom there are birds out among you sitting on vines and there are rope bridges you can walk on that are behind waterfalls. very awesome for any age.
In here also you can walk on a dock of sorts and there are crocodiles and alligators in the water, you walk a little futher and you see a beaver home (the back on one side and the inside on the other (there is glass there so you can see in).
The aqaurium has lots of fish and a jellyfish tank, they have penquins that are in an enclosed glass area and it snows inside there its so awesome, you can walk down a ramp and see them swimming in the water.
I highly recommend going there, when we were last there it was 2 years ago and they were just finishing the cat house, also one of the female gorilla's had had a baby and it was clibing the ropes. The whole ZOO is AWESOME. You can look it up on the internet and see the web cams they got in the penquin exhibit, they have a couple more cameras in other ones but I can't remember which ones. I know it's not quite what you are looking for but I thought I might mention it.
The other place I want to take my kids is ceder point (it's like worlds of fun) it is in Sandusky, Ohio I know what you are saying about the airfare and the amount it cost's we have 6 in our family quite younger in ages though atleast 3 of them. Hope this helps a little W.