I'm sorry for your loss Cody. I can't imagine how devastated you must be. I just joined today to be able to respond to you. I'm planning a quick trip to disney in January for my daughter and I. We both love disney, this will be her 5th trip to disney and she's just turned 4! So I have quite a bit of experience doing disney with a toddler. It's great that you will have help with the kids. Be prepared to split up if necessary. One child may need to go back to the room while the other two are still having fun. Have you been to disney before? Are you staying on property? With three toddlers, I wouldn't plan full park days. Maybe plan on spending 4 or 5 hours at the parks. Go in the morning to the parks and hit your fastpasses, maybe pick one or two more things to do or see, then back to the resort for nap time and just hang by the pool in the afternoon. At this age, they may or may not like the characters, same with the rides. Just try to enjoy whatever they do like, even if that is running around a park bench or staring at glitter in the concrete lol. The highs match the lows, your kids will have the most magical experience of their lives, they also might melt down on main street. Just try to keep in good humor.
I lost a spouse to divorce, not death, so it's no comparison really. But the first time at disney post divorce, it was hard for me to see happy families together, especially fathers with daughters the same age as my daughter. I don't know that there's anything you can do to prepare for that but I guess just be aware that you will probably have similar feelings. I'm sure this trip will be difficult while grieving, I hope that you are able to find moments of joy.