I'm sorry for your loss OP and that you have had the added stress of an investigation which must make everything even harder to bear.
Before I retired I was heavily involved in Governance in the Trust I worked for and I did reviews of deaths and adverse incidents as part of my job for quite a lot of years. Different Trusts do things differently of course, but I can give you some idea of the process at the organisation where I used to work.
Serious Incident reviews aren't done by the people who were actually involved, but by someone senior who didn't look after the patient themselves but has enough knowledge of the clinical area and who has been trained in investigation, root cause analysis etc. In our Trust we would generally have two investigators, often a consultant and a senior nurse. We would review all the written records, do interviews or get written witness statements from everyone who was there to create a timeline, assess what contributed to whatever happened, assess what was avoidable or not, whether there were any mitigating factors etc, and then make recommendations on any improvements that need to be made as a result. In our Trust the report would then all be looked at by a panel including various directors who would decide whether there were any disciplinary issues or anything needed to be reported to higher bodies etc.
Our process involved there being someone with the specific job of communicating with the family to keep them updated on what stage we were up to, but we tended not to hold a formal meeting until the report was complete. I would normally expect the person who led the investigation to be the one who talks to the family, but it might also be the Head of the relevant department or the Medical Director of the Trust, often with a senior nurse present too. I can't recall ever having anyone legal with me ever, though that's not to say it doesn't sometimes happen. We would go through the main findings of the report - the timeline, what we've found and what actions have been taken as result, and do our our best to answer any questions that the family had.
Our normal practice was to offer a copy of the investigation report and to give the family the option of further meetings once they have had a change to digest what's been said.
There can be a lot of information to share, and of course it can be upsetting to recall events so it is probably a good idea to have someone along with you who can support you. Don't be afraid to ask for a break if you need one, or to ask questions if you are unclear about anything. You might not think of all the questions you have at the time so if you aren't offered a specific follow up meeting, make sure you have the contact details of someone so you can get back in touch with them if you have later questions. The report should be written in such a way that a non professional can make sense of it, but there will probably be a lot of technical information too so it would be totally reasonable of you to want time to fully understand it.
It can be a very draining and emotional thing to have to go through so please look after yourself. Don't rush into any decisions about whether you want to take legal action or not. Take your time to process everything, ask questions, talk to other people, and be kind to yourself. I hope the meeting goes as well as it can, you get the answers you need and you don't suffer any more avoidable distress.