Ooo tough one!
When I changed Madison to her cot I weaved her bassinet mattress though the head of the cot, and placed a queen sheet under the mattress and draped that over the side bars so it was like her bassinet
I think letting your bub play in their for as long as possible a few times a day is a great idea.
I still do this with Madison as it reinforces the idea her cot is a happy place.
Just be sure to take bubs out as soon as it stops being fun..
& Good luck!