I vote for taking the baby. We went when our daughter was 2 months old. We're headed back in two days, she'll be 8 months old. There really isn't much to lug. I breastfeed, so there's no food to worry about. (The current AAP reccommendation is to wait until 6 months for solids so you won't have to worry about food. My daughter really isn't into solids yet even at 8 months). I use a sling, so she doesn't need a stroller. (We do take a stroller for our 3 year old though). I have a backpack that is a diaper bag which worked out great - even when both kids were in diapers for our last trip. I do have a distractable nurser this time. My son would nurse anywhere - I even nursed him while I was running in a half marathon once! But my daughter gets distracted. There's baby stations if needed for that. I may even throw in my hand pump just in case. We co-sleep so there's no pack n plays - though many hotels have these.
However, if you're pregnant, then there's a lot of rides you can't go on. I did go to the fair when pregnant with my daughter and it was tough to just sit back and watch my husband and son do the rides without me. Also, I get huge when pregnant. I don't mean the normal huge, I mean super-huge. I gained at least 70 pounds in each pregnancy and I'm barely 100 pounds when not pg. My babies were born at 10+ and 11+ pounds. I had terrible vulvar varicose veins last time that made standing for 5 minutes tough - starting at only 22 weeks. I also had hypermesis (severe sickness) last time that didn't end until 18 weeks. You don't know what your pregnancy is going to be like. I'd definately suggest waiting.