Well, I wouldn't try walkng from the centre of Amersfoort (Amersfoort central station). You could walk from Amersfoort Schothorst (about a mile).
Both stations have regular bus services to the meet (number 12). Trains back to the airport are every half hour all day; you should have no trouble getting a train back to Schiphol all day. If there is any problem then I will drive people out to Schiphol after the meet, so don't worry!
If you want to look at train times, check out
the NS timetable and look for the English language version of the page. Buses are also every half hour.
One of the few remaining Mk1 owners...
#00015