Doom day on holiday

The hotel should be able to store your suitcases. Just pack a backpack for essentials for the day until you transfer to the airport and sort the bags/carry in a space in a corner of the hotel lobby or airport area before screening.

I have never been in a decent hotel, which doesn't provide this. You will be up early, nab sun beds and a couple of parasols, camp out by the pool. Decent lunch, and you will need to get showered and dressed by about 4 pm. It's not ideal but will be fine.

Do you travel much? I don't mean it to sound catty but this is the type of thing I would be concerned about and I don't travel much. Most hotels will happily keep a hold of your luggage if you have a flight later than check out. You just need to check with them though. I'd keep a separate bag so your nappy bag with a few extra bits that you can have to hand. Use sun loungers with parasols and assuming inside of the hotel has seating areas retreat there if it's too hot for the baby. It's your last day so might as well make the most of it. You could head out to lunch or explore whatever nearby the hotel.

Check with the hotel. You should be able to leave luggage with reception and there may be a courtesy room with a shower that you can use.

Use the pool for a few hours, visit local shops or play park, have a nice lunch, shower and change for the plane, play some games in the hotel lobby (hopefully air conditioned).

You just need to separate your packing so you have everything you need for the day and the plane journey easy to access.

It's doable and there will be lots in the same position as you.

Why don’t people read the OP?

Most hotels have a luggage room and somewhere you can have a shower. I usually try and book a late check out but it might not be guaranteed in peak season.

Can you pay for an extra night even though you won't be staying the whole night? It will be worth it just to be able to use the facilities.

Leave your luggage and go out - it’s most holidays.

We went to the beach has lunch then a last walk round the shops.

There might be air conditioned kids places like ball parks you could google -

Can you ask the hotel if they have a later check out for you. And also if they have luggage storage if not so not lugging this about.

If too hot and don't want to be by the pool all day is there an air conditioned outlet mall nearby? We did this once on our day travelling home not because of heat but due to rain all day. Hung out at shopping mall, there was an indoor soft play for the kids. Had lunch etc then got taxi back ready for hotel transfer. Was able to leave suitcases at hotel.

Surely you can leave your luggage in reception?

Use the pool, wear her out a bit and try to get her to sleep on a sunbed under the shade. Find a nice air conditioned restaurant for lunch with the buggy.

Talk to the hotel about leaving your luggage somewhere, keep a smaller bag with your bits for the day and treat it like a day trip.