This is high risk when it comes to your individual wellbeing and your relationship as a whole. If it was going to work out it would come from excellent communication, honesty and trust and a bunch of reading of the literature around that lifestyle.
‘Normal’ is a social construct that is meaningless and often harmful to those who aspire to it and oppressive in the societies that sanctify it. Human relationships and sexual identities are on a spectrum and these types of relationships and identities are as legitimate/normal as any other.
You wanting to make him happy isn’t likely to result in it, if just manifested in you being passive, uninvolved or un-interested in his decisions, which may cause harm to both of you and your relationship. This needs proper discussion.
It’s absolutely fine and healthy to put limits on what sexual activity you will or won’t engage in or what you both wish to try out but this takes a lot of communication and a strong resilient relationship. These can also be negotiated and will naturally change over time.
Without prying, so no need to reply, I’d wonder how your sex life /marriage is currently and how happy/content you both feel.
I’d also consider/talk through the following:
Is having sex 1-2 times a month enough for you both, who initiates it? Has it always been like this? How are your sex drives? How confident are you both sexually? How is the sex? Does it satisfy you both? What are each of your fantasies, have you shared them? Have you tried exploring them as a two some? What is it he wants to do with a male partner?
Moving to inviting other people into what was a monogamous marriage feels quite sudden move, is the deep end and again high risk.