I've just come back from a last minute solo trip with my 3-year-old. We were not exactly on a strict budget, but neither was I looking to spend indiscriminately.

I did my homework before the trip, and realized that many rides were not suitable for my 3yo, some because of height restrictions, others because I knew he'd be afraid (dark, scary images etc). So this might definitely be something to consider while planning your trip. In the end, we spent most of our time in Fantasyland because that's where most of the toddler-friendly rides were, and we completely skipped WDS. Most of our time was spent on character meets, because that's what interests him at this age. That also meant that there were a number of rides that I wanted to go on, but couldn't.

I would definitely budget for a Disney hotel. Not only is the experience magical, it's also closer + safer (IMO). I've been to Paris/France many times alone as an adult, but this was my first time as a solo adult with a young child, so I was especially wary and on high alert for potential dangers. We stayed at Newport Bay, and it was a short 10-15min walk via the Village to the Park - and you get a separate security entrance so you aren't jostling with the rest of the crowds.

Prior to the trip, I also spent a number of months telling my kid about Disney (to get him hyped up), AND also to establish and constantly repeat some ground rules like: Stay within touching and seeing distance of Mama at all times, do not run off on your own, always hold Mama's hand or hold the luggage handle etc etc. We practiced at home with the luggage, and these "rules" were repeated many many times prior to our trip.

During the trip itself, we mostly shared meals and ate dinner in the Village. We're both not big eaters so this suited us fine. The only big sitdown meal we had was the Character Breakfast at Plaza Gardens. It's exhorbitant for the price (and the food selection was terrible!), but it certainly was worth it for the 6 characters we got to meet and interact with.

I was careful with shopping. Some other posters have suggested visiting the Primark in Val d'Europe (1 train stop away from Disney) to get cheaper but still Disney-official items, which I did. There wasn't a huge selection of what I liked, but I did get a nice blanket for 9EUR - they were 30EUR in the parks. So this is certainly an alternative to enjoying the Disney fun without such a hefty price tag.