She should be in her second trimester by April. I can't speak for everyone, but that's when my morning sickness stopped, and I actually started feeling great! (If she's due in September, she's pretty much on the same timeline as my first pregnancy, when I went to WDW in April) She won't be unwieldy yet; I wasn't even showing very much. She's probably going to be wearing maternity clothes for the first time, so she won't be sick of them yet. She might get tired more easily, although I didn't notice it too much. The food choices are much better than they were back in 1983; you couldn't buy bottled water or much in the way of "healthy" food.
My suggestion would be, barring any complications, to go and enjoy your last fling as a childless couple. :lol: