"please join us in congratulating" is a correct and usable sentence in written English. You can use it to politely invite someone to join you in congratulating someone for their accomplishment or achievement. For example: "Please join us in congratulating Sam for receiving the top score in the math exam!".
Congratulations to Dr. Witney and Dr. James! Please join us in congratulating Aaron Mayer and Surya Murty who received 2015 NSF Graduate Research Fellowships.
Please join us in congratulating her.
Please join us in congratulating Mia.
Please join us in congratulating Andrea!
Please join us in congratulating Balaji!
Please join us in congratulating Gene on his appointment.
Please join us in acknowledging and congratulating our 2017 – 18 incoming Alumni Scholars.
Please join us in acknowledging and congratulating our 2016 – 17 incoming Alumni Scholars.
Please join us in acknowledging and congratulating our 2014-15 incoming Alumni Scholars.
Please join us in acknowledging and congratulating our 2018 – 19 incoming Alumni Scholars.
Please join us in acknowledging and congratulating our 2015 – 16 incoming Alumni Scholars.
Since I tried Ludwig back in 2017, I have been constantly using it in both editing and translation. Ever since, I suggest it to my translators at ProSciEditing.
Justyna Jupowicz-Kozak
CEO of Professional Science Editing for Scientists @ prosciediting.com