Joy in the Lord is not what our world means by "fun". IMO If you trick a bunch of people into making some kind of sinner's prayer, telling them how fun it'll all be, you'll lose most of them the moment the worldly "fun" stops and any kind of persecution begins.
The church should not, and cannot, compete in the "fun" department. For the unconverted, sin is fun. Selfishness is fun, fornicating is fun, drunkeness is fun. All fun, fun, fun.
Yielding ourselves to the Lord Jesus is not, and never has been, the most entertaining option.
I think this emphasis on "fun" is false advertising - all too often leading to false conversions.
Dying to self cannot be made fun with silly songs, crafts, and dancing.
---
BTW, what's wrong with serious Bible study? Can it really be improved with a few whoopee cushions and silly faces?
Sobriety is a virtue.
2Corinthians 5:13
For whether we be beside ourselves, it is to God: or whether we be sober, it is for your cause.
1Thessalonians 5:6
Therefore let us not sleep, as do others; but let us watch and be sober.
1Thessalonians 5:8
But let us, who are of the day, be sober, putting on the breastplate of faith and love; and for an helmet, the hope of salvation.
1Timothy 3:2
A bishop then must be blameless, the husband of one wife, vigilant, sober, of good behaviour, given to hospitality, apt to teach;
1Timothy 3:11
Even so must their wives be grave, not slanderers, sober, faithful in all things.
Titus 1:8
But a lover of hospitality, a lover of good men, sober, just, holy, temperate;
Titus 2:2
That the aged men be sober, grave, temperate, sound in faith, in charity, in patience.
Titus 2:4
That they may teach the young women to be sober, to love their husbands, to love their children,
Titus 2:6
Young men likewise exhort to be sober minded.
1Peter 1:13
Wherefore gird up the loins of your mind, be sober, and hope to the end for the grace that is to be brought unto you at the revelation of Jesus Christ;
1Peter 4:7
But the end of all things is at hand: be ye therefore sober, and watch unto prayer.
1Peter 5:8
Be sober, be vigilant; because your adversary the devil, as a roaring lion, walketh about, seeking whom he may devour:
1Timothy 2:9
In like manner also, that women adorn themselves in modest apparel, with shamefacedness and sobriety; not with broided hair, or gold, or pearls, or costly array;
1Timothy 2:15
Notwithstanding she shall be saved in childbearing, if they continue in faith and charity and holiness with sobriety.