Connecting ipad to monitor and usb keyboard and mouse

Hello, ive connected a monitor to my son’s 7th gen ipad via the digital av adapter. Ive now realised i need to connect a wireless but with usb receiver keyboard and mouse. How can i achieve this? The multi adapter i researched on line with usb port does not support his ipad. This would have been perfect if it did. The digital av adapter has what i believe is a charging port, however was wondering if i can connect another adapter to connect the keyboard and mouse. Alternatively seeking recommendations of pure bluetooth keyboard and mouse with no usb receiver. Thanks