Couple starting on the journey seeking advice

First time poster here, wife (37) and I (44) have decided after a couple of years of talking to try an MMF threesome (not MFM). She's not quite ready to consider involving a woman so couples are out of the question.

We have an absolutely rock solid relationship so we are not concerned about jealousy. Although I've got no experience with guys we decided on an MMF as I'm open minded and we both get to play but it will mainly be about her.

Worked through boundaries and as essentially she (and I) want the third to be there to support us and we don't want to have much of a focus on them (for a first time) so we will be looking at getting a professionat that way even if we change our mind mid-session there will be no feelings to consider.

Pretty sure we've thought of most things and been through the advice in here. Main question is if there is anything that throws a flag in our approach as it's sort of jumping in the deep end?

P. S. We considered starting softly at clubs but both need absolute discretion for the moment