Gent would be an ideal base. Only around 3 hrs from Utrecht with using the Intercity service. Good for the afternoon and evening on the day of arrival. Have the next day for Brugge, which is only 30 mins away.
You should be back near Schiphol airport the evening before departure. The slightest problem on the line or with the train between Belgium and Schiphol airport, which are not unknown, and you're in deep trouble.
Tickets for the Intercity service (have Gent-Sint Pieters as destination) for 1 Sep are a fixed EUR 35, and EUR 26 for the return trip on 2 Sep, for any train running that day (the Intercity doesn't come with reservation). You can buy them online (Belgianrail or NS International), but also at the railway station (with perhaps EUR 1 or 2 handling fee).