Since you have a lawyer, it is always advisable to inform him/her of your intentions and have an agreement on it. Going behind the lawyer's back could lead to termination of representation, because they may be caught unawares. Also, you do not want to send anything which the lawyer has not verified first.
My approach in such a situation would be to first look at your country specific guidelines/checklists, etc and bring to the lawyer's attention. Ask his/her opinion but you can also say you believe it should be sent along with additional relationship proof. Let them vet the photos and other evidence and ensure they send it to the visa office(ask for tracking number). If you feel comfortable, express(very nicely ofcourse) that you feel disappointed that these were not done from the outset as you retained him/her trusting their legal opinion and their expertise. Reassure him/her that despite this "error", you appreciate his/help and still trust their expertise(even if you have a few doubts... lol... you are relying on him/her and you want them 'happy' even if you think they are not that great. lol) Then ask what can be done in the form of some kind of compensation - it could be a discount on your legal fees, or no payment for him having to vet this evidence and send out.
For future reference, it's important to read and do your best to understand the guide/checklists/rules yourself even if you have a lawyer. Lawyers are afterall human and can make mistakes too even when they mean well.