Reddit mentions of Illco Walt Disney's Mickey Mouse Vehicle Play Set

That's because the toys you're thinking of were knock-offs of Fisher Price Little People. They had the same bodies, but Disney heads.

I think if you search for "Illco Mickey Mouse Vehicle Play Set" you will find what you're looking for for the figures. I don't know which set you had.

There are a few copies on ebay, still in box, of new old stock. (Those aren't my auctions, I just found them when I was searching for a picture.)

Or:

https://www.amazon.com/Illco-Disneys-Mickey-Mouse-Vehicle/dp/B00GRAFAUM

The amazon listing, with picture.

I don't know about the slide. You might have used those figures with the Illco Loop the Loop playset or Roller Coast play set. I think the vehicles were compatible.