My kids are much older now, but when I started doing Marathon Weekend my youngest was 4 and oldest 8. They have been with us for every MW since. It is doable with kids, but there has to be compromise in terms of vacation and running. Our agreements are that I get back from the 5k and 10k as quickly as I can and we go straight to the parks after I clean up and eat. Over time we have used the variations of Fast Pass, Genie and
Lightning Lane Multi Pass to prioritize the things we want to do together. Earlier dinner and then back to hotel. From end of race until after dinner I would stay focused on being a dad on a Disney Vacation, but after dinner the family let me be a runner getting ready for next race. They would watch a movie or go to the pool and I would get ready for the morning and get to bed. Most years after the Half we would either go really light or just have a resort day. And after the Marathon I was expected to suck it up and play with the family until fireworks - that got a little rough…
Honestly though it has worked out pretty well. As my girls got older one became my running partner and does the 5k,10k and Half with me. And now that they are older they often stay at the parks much later than my wife or me anyway. We still prioritize time as a family from late morning until early evening. Walking around the parks between races has been really helpful for my legs and as long as I don’t over do it I have found it to be really beneficial. I think it can work.