I'm a little further down the road with my DC than most of the posters here.
DD has just passed her Grade 8 ABRSM singing - she took grade 1 - 5 then missed out the rest. She has also passed grade 5 theory, grade 8 viola and grade 7 piano over the past couple of years (plus the GCSE music AS and about to take A level!!)
She is intending to study music at uni and wants to be an opera singer if her voice continues to develop.
She regrets taking ABRSM exams as she now feels that the emphasis was on results not repertoire - now she has reached a higher level she has come to realise that a good repertoire and ability to perform well in sight reading are the most important things for continuing with music as a career. Her current singing teacher prefers trinity guildhall for these reasons as well.
It is great though for younger children to have something to aim for - that first Grade 1 result was magical for DD! But it is much better to take things slowly and avoid being forced into taking exams - I think the term is "singing/playing around your grade". I remember the pressure put on me when I was younger to take music exam after music exam - it was very stressful.
DS has also has singing lessons - both sing in choirs at their respective schools (school choir, choral society and chamber choir) and I feel that the singing lessons helped them both with confidence issues when they were much younger.
It's great to sing!
PS: recorders can be good - I still play! & I'd love to play the ukelele