No, it's not incorrect.Hello,
The key to a test from my book gives the following answers:
It's my mum and dad's golden wedding anniversary next weekend. We've been arranging a surprise party for the last three months. We've booked a room...ordered a cake...received over 50 replies to our invitations. Mum and Dad suspect we've been planning something special, but they don't really know what. I know Mum has been thinking very carefully about their outfits. She's bought a new dress and ....
A couple of students have chosen 'have planned' and 'has thought". Although I'd go for the progressive, I don't think the present perfect is incorrect. Or is it?