Пре­об­ра­зуй­те, если это не­об­хо­ди­мо, слово NOT FORGET так, чтобы оно грам­ма­ти­че­ски со­от­вет­ство­ва­ло со­дер­жа­нию тек­ста.

After the tour they had so many questions for the senator! I could not help smiling at the interesting topics they raised. I’m sure they __________________ this great experience for a long time...