Transition from grow bag to a doona

My DS is now 3 and still sleeps in his gro bag (18-36 months). He's never really slept with anything else on but the grow bag (and some night clothes under the bag of course lol), except in summer on really hot days where I put a flat sheet over him (which always got kicked off). I really want him to get used to sleeping under a proper little doona when he goes into his big boy bed soon. How do I go about it when he kicks everything off? He's a hot bod like his dad, whenever he ends up with us he often kicks off the doona while I'm freezing! Any advice would be greatly appreciated :)

I stopped using grobags when my boys were taking them off.
I just put them into bed in winter in all in 1 fleece suits with feet, that way if kicked doona off wouldn't get too
Cold. Had to
Stop using on DS1 when stopped wearing nappy at night as was having accidents trying to get it off.

Both of my boys get very hot and sweaty at night with doona, I always check on them before I go to bed and must nights cover them up
Again. Both have moved to bed around 2.

Subbing as I need advice too.

we did it with ds in summer - well, e got rid of the grobag one hot night and then when it got colder we just used the doona. I have no idea.if they're any good but don't grobag make some sheets/a cover that zips to the bed somehow? part of me thinks money-making the other half thinks great idea!

Ideas appreciated here too, DS has been in bed since 15 months after climbing out of cot, and gave up with grobags then as seemed dangerous with him trying to walk and climb in them. He refuses any sort of cover on and is just getting cold over night - he wakes at 5:30AM (and won't go back to sleep) and am sure is due to cold - going to try the all in one suit tonight, but am just hoping that when it actually gets really cold he will permit a doona on him.

Our place gets really cold overnight. In Winter, we put DD in pjs and then all in one suits with legs over top to keep her warm if she comes out of her blankets. We also tuck the doona (and blanket on top) in between the wall and bed to reduce breeze coming in on that side. The other side of the doona is free.

DD is useless with a doona. She outgrew her grobags and was in her cot with the side off, so I didn't get her new ones because of the cost and the fact that she was climbing in and out.

If it's really cold I can put the doona on when she's really asleep and she doesn't notice lol. But generally less than an hour later I hear frustrated crying, wriggling and moving, and she's kicked it off or turned sideways. She just won't have it!

So I put her in a onesie with feet, with flannelette pjs over the top. She hasn't gotten cold dressed that way, and I just have to hope that one day she'll get used to the idea of a doona.