Short answer: Yes, with help.
What works at this age: Sort and Story are the sweet spot at five — sorting fonts by feel needs no reading, and the stories work read-aloud with a grown-up. Detective is playable sitting together, and the Poster Studio is a hit with someone driving the mouse alongside them.
What’s harder: Typing and FontRun assume some letter-recognition speed a typical 5-year-old is still building. Expect them to watch those modes more than play them for the first while.
What they’ll get out of it: Letter recognition, comfort in front of a real keyboard, and their first sight words — plus the beginnings of noticing that letters come in different shapes and moods.
What to expect in the first week: Short sessions, 15–20 minutes, with you next to them. They will want to hatch fonts into the Fontdex faster than they can read the facts — reading those aloud is the game at this age.
Font Quest is a Mac & Windows desktop game — $14.99 once, no subscription, no account, no ads, and it works offline. If it isn’t a fit, there’s a 30-day refund, no questions asked.