Keeping loft conversion as cool as possible?

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So, stupid question alert (in my defence I have an 8 week old baby!) but we have a loft conversion. We have 3 velux on one side (the side of the roof is in full sun all afternoon/evening) and a large window on the other side. We also have a window at the bottom of the stairs (gallery landing). There are blackout blinds on the veluxes, and curtains on the window, and we need to get a blackout blind for the window at the stairs.
Temperatures can reach 27 degrees when it's 22 out, so I really want to try and keep it as cool as we can. Are we best off having the windows 7 velux open all day so there is as much ventilation as possible (with curtains/blinds shut) Or to keep them closed and open later in the evening about 7? (we are currently going to bed about 9 as exhausted with little one) Can't keep the largest velux open all night as it's above the crib so a bit draughty.

Thanks for advice

I would keep the 3 windows that get sun all day closed and blinds down. Other windows open with blinds down. The key is to not let too much sunshine in.

I'm an Aussie and we would spend summer walking around in the dark with sunshades pulled down on all windows from about November through to Feb!

I keep our blinds closed at the front of our house here in the UK as it gets direct sunshine all day and the back windows open that are in the shade.

When the sun goes down a bit you could open the 3 windows if it needs some air.

We keep all the blinds in our loft conversion closed all day and then open in the evening.

I have to say though, the only thing that really fixed it was having aircon installed up there. That was amazing

Closed with blinds drawn during the day and open in the evening when it's cooler. We have two huge windows on lower floors which are east facing and I keep the curtains closed in the day otherwise those rooms are like ovens.

I'd use the blinds Velux external blinds, which stop the heat getting in through the glass in the first place and are much more effective at that than internal blinds. You can install them from inside just by flipping the window over, and they're cheap.

Other than that, I'd do what @LegoBitcho suggests and also put a fan near an open window to circulate the air.