@LibbyVonTrap
Thanks everyone, I’m thinking I’ll just pull the mattress onto the floor when she sleeps over. I’ll be completely baby proofing the room along with a stair gate.
She won’t be a baby that long anyway.
One thing I’d suggest is trying to avoid making it ‘your granddaughter’s room’. There may be future grandchildren and you really don’t want to end up in a situation where you’re reallocating a room that’s been ‘hers’ in everyone’s minds.
Create a lovely, comfortable, safe space for grandchildren to stay (and other guests). But make it somewhat generic for future changes.
I say this because of what I’ve seen in my (truly awful) MIL, and (while I don’t for a second think you’d play favourites like she does) it does become trickier once a room has a single owner in everyone’s minds. My stepdaughter has a bedroom at MIL’s house. This is referred to as ‘SD’s room’. When SS came along, he didn’t get a room. And it stayed SD’s room (MIL’s hugely favoured grandchild in every single way). He is expected to share with his father instead. While ‘SD’s room’ remains sacred. My husband offered MIL a bunk bed for the kids but she outright refused because ‘SD needs her own room’. For context, they share a room at all other times. It’s only at grandma’s that SD gets her own special room and SS gets nothing.
Obviously no one but my MIL would be so utterly horrible (she is a specialism of terrible) but it does become trickier if you start allocating anything.
It might be best to think about a nice, fairly future proof guest room that’s primarily about accommodating grandchildren.
Do you have room in there for a double? It might be more flexible. My gran has a double in her spare room andi remember sleeping in it regularly (with my sister) as a child