Belize with 2-year old
 

our family is going to a wedding this May in Belize. The wedding will be in Placencia but we are hoping to extend our trip and visit some other parts of Belize as well. My daughter will be 2 at the time. Looking for suggestions.

Are you interested in inland or water-based places and activities? General budget? Lots of 1st time visitors split between the Cayo district and an island or beachy place; the most popular of those are Ambergris Caye, Caye Caulker, and Placencia. It will likely be really hot in May so picking places with ac and/or a pool might be wise with a little one. My kids were 17, 18, and 20 the 1st time we visited Belize so I'm not much help beyond that - sorry! You can check out our photos, blogs, and travelogues below if you're interested. Happy trails!
http://www.flickr.com/photos/staceyholeman/collections

Placencia is a great area to base for both beach and mainland day trips. If you want to split your trip between beach and mainland, look at the Toledo district, closest to Placencia or the Cayo district in western Belize. 45 ft docile whale sharks congregate off the Placencia coast in May around the full moon and up to 10 days afterwards. Incredible to see while diving or snorkeling.

www.cavesbranch.com tonnes of fun or maybe orange walk area

I lived in Belize from 2000 up to last year, on Caye Caulker. I have seen a lot of Belize, and if you are already seeing Placencia, then don't miss going out to the cayes.
Caye Caulker is really wonderful. No Cars, sandy roads, golf carts and bikes. A very strong family community. There are kids everywhere. It's one of the few places in the world where your kids can play and you don't have to worry about traffic or other normal dangers. The cost of hotels on Caulker are on average HALF as much as in San Pedro, Ambergris Caye. And the other great part about Caulker is that you can take the water taxi to the mainland and go to some of the famous Mayan Ruins tours as well as take a quick boat trip to the reef to see Shark Ray Alley (these are nurse sharks...NO Teeth!) The water at Shark Ray Alley can be as shallow as 3 feet, so it's an excellent snorkel location for all ages.
For Shark Ray tours, the best is to wait until you are on Caye Caulker, then just stroll along Front street and stop in an talk to the little snorkel shops that you will find on every block.
For Mayan Ruins, the best way I have found to do this is to book your tour on-line and take the water taxi to the city to meet your tour. You will find that this way costs you about half the price of booking it from the island, this is one of the best travel tips i have!
Look on-line at http://www.caribbeanshoretours.com/BelizeShoreTours.htm for 3 different mayan ruins tours. My preference is Lamania, but all the ruins are worth the trip. Also, you can ask which days are cruise ship days, and book a non cruise ship day. Best way to avoid the crowds!