Good day
The importance of starting an interest group, whether that be around sports, baking, photography, painting, etc. as a form of ministry, should all be centred around reaching those who are yet to know Christ by building relationships with them, and forming stronger relationships with the existing members - all the while sharing and demonstrating the love of God to all.
The purpose for all church groups/activities, in my opinion, should be to invite the lost and provide a platform for Godly fellowship (relationship building)
The purpose is also to be all inclusive, not just doing things with our buddies/friends all the time, but rather extending that invite to others, with the purpose of getting to know them better and being a vessel through whom the Holy Spirit can speak through us to that person.
So whatever the activity is, even watching a movie, truth be told - we don't HAVE TO watch a movie with anyone, nor do we need to invite anyone - anywhere for that matter! Sometimes the activity may not even be something we enjoy doing, but again, we should ask ourselves if it's always about us or if whether God has an agenda in us meeting together. It may not be something we enjoy, but maybe the other person prefers it, so we make ourselves available to be used by God to be a blessing and an encouragement to the other person.
Therefore in all things we try and adhere to God's agenda.
We must take Paul's approach:
I Corinthians 9:19-23 NKJV
For though I am free from all men, I have made myself a servant to all, that I might win the more; and to the Jews I became as a Jew, that I might win Jews; to those who are under the law, as under the law, that I might win those who are under the law; to those who are without law, as without law (not being without law toward God, but under law toward Christ), that I might win those who are without law; to the weak I became as weak, that I might win the weak. I have become all things to all men, that I might by all means save some. Now this I do for the gospel’s sake, that I may be partaker of it with you.
There are things we don't like doing. Things we don't have to do. It may not even be fun for us - but for the sake of the lost - we do them.
Remember that God's intentions (or desired outcome for something) is inspired by His purposes, meaning that His intentions for your group are driven and inspired by His purposes - and His purposes are always about people. Therefore His intentions with your group is to see it develop into greater things that He may have planned for it! The goal or objective is always bigger than us. The impact we make on the lives of others, also far outweighs us. The people we reach and influence, will reach and influence others (this will continue and carry on, possibly even past our time on Earth) - therefore the input and effort/diligence we put in now, has a far greater impact compared to what we see right now. We should always maintain an eternal perspective on the tasks or assignments God asks us to do for Him ... millions could be reached through your obedience, faithfulness and commitment to His agenda and His will. Amen!
Stay Strong in the Grace of God my friend.