We went last year in the October half term. We were lucky, with an October heat wave, so temps were in the low 20s some days, rather than teens.
Activity wise, all the things like paddle boarding/pedalos had shut shop for the season.
Bike hire was still available, and our children loved all the cycle routes. Our sites pools were open for the first half of the week- seems to vary from site to site, so worth checking.
On site Activities like football clubs, archery etc were still open.
Days out wise, the theme parks appeared to be closed, but we didn't check, not really our thing.
We did day trips to Verona and lots of towns around the lake. The cable car up Mt Baldo was great and has good availability even late in the year.
The ferries still run, just on a reduced timetable.
Nearly all the restaurants were still open, just quieter, which suited us.