12 hrs in UK

You’ll definitely need to book a hotel for the night. With your arrival times and two young children that’s where you’ll be spending your time.

Not feasible to travel into central London – not for me anyway.

I assume both flights are at Heathrow?

Book the hotel at the airport you are flying out of and then go into town if you feel like it. The Big Ben clock tower (whatever they call it officially) by the Houses of parliament is covered up for restoration work though through 2022 or something like that.

we are flying into Heathrow and out of Heathrow. it will be the same terminal. My idea was that we would venture out to Central London and spent a few hours and take the tube back to the Hilton Hotel at Heathrow. I did this yrs ago and felt confident and safe, is it the same now, to venture out at that time of the evening and come back to the airport.

Arrive at 7pm, out of airport at 8pm. Check into airport hotel by 9pm. An hour on the tube to London now it’s 10pm. Walk around for an hour. Then tube back to Heathrow by midnight.

Yes you could do it, your husband/wife could do it, I might be tempted to do it, but what about the 5 year old?

The Big Ben clock tower is known as Elizabeth’s Tower. Will be in scaffolding for another 2 years.

How well do your children do on short hours of sleep? You'd likely not get into central London til 9 pm, so most of the tourist sites would be closed. Of course, you could just walk around, and perhaps get something to eat. Then it would take about an hour to get back to your hotel. And be up in the morning for check in at the airport by about 7 am. I wouldn't have done it with my kids, but perhaps yours are more resilient.

the flight is a short flight, 4 hrs only, the hotel is about a 10 min walk from the terminal. we will have a stroller with us, but we are thinking of checking into the hotel after we visit the city. my kids have been traveling since newborn stage, they both are well behaved and love traveling and seeing the outdoors. is there a locker we can use to hold our carry on before we check in to the hotel. my concern is safety for the most part. your inputs are well appreciated. my husband doesn't know the city, so all is on me as far as planning. i'm getting the feeling that most of you wouldn't do it, for reasons of tiredness or short timing. I'm trying to get the feel of safety concerns. my idea is to get on the hop on hop off bus if it is still running, if not then just get of the tube, visit Buckingham Palace, Picadilly Circus and Trafalgar Square. we don't have to do all but that would be the plan.

With children that young I'll be checking into an airport hotel, getting some sleep before getting up early to be at the airport three hours before the flight. You don't have time to visit London.

Safety isn't an issue, what you feel you could achieve is.

we will arrive via BA from Santorini JTR at 7pm London time,

Do not forget to factor in the fact that is 9PM ( when you land) in Greece where you will have been. The kids body clock is going to still be on Greek time. By the time you get into London, it will seem like midnight to them.

Safe and feasible

Probably safe; feasible, not so much

my $0.02

No, but perhaps you could change your 2nd flight to be a whole day later and get out and about that next day if you really want to see things with the family while you're there. The opportunity could be worth any change fees, while you're there, and since you live so far away. That way a lot more would be visible during the daylight hours too.

thank you all for the recommendations. Changing flights is not optional at this moment, as we will have to get back to the states for my children have to start school. perhaps we will do a separate trip to the UK in the near future. Thank you all again for the input.