Shannie - I’m not too sure where the Holiday Inn is but the obvious first things to do if staying near Kings Cross (and if you are HP fans) would be to go get your photo done on platform 9 & ¾, you will spot the queue! It is next to St Pancras too, which is what they used for the exterior station shots. If you are doing the Eye Spy book – you are also right behind the British Library. The I Spy book we have is a red michelin one that was £2.50
So I would get the northern line from Kings Cross down to Tower Hill tube, there is an exit that brings you out opposite the Tower of London, its well signposted! Tower bridge will be to your left and you can walk all the way around the outside of the Tower without going in (unless you want to) you should find Beefeater or two opposite the TofL shop. When you have finished looking around, come out onto Lower Thames Street and turn right, you will seeOld Billingsgate Market & you should be able to see HMS Belfast on the Thames, turn right up Monument St and follow this to the actual Monument ( the great fire of London) this is worth a visit, has great views where you will be able to tick off lots of sights St Pauls, the shard, the gherkin etc, not too expensive and you get a certificate at the end! – but might not be worth it if you are doing sky garden! . Pudding Lane will be just behind you on your right and there’s a small plaque underneath the street sign.
I would go down Pudding Lane, turn right onto Eastcheap, then left onto Philpot Lane for the sky garden.
If you wanted another museum to do near here, you are not far from the Bank of England museum. It’s free, not too big and actually quite interesting! There is a trail for the kids to do, but check its opening days. You can try and lift a gold bar.
After Sky garden I would go back down Eastcheap, but turn left onto King William St and cross London Bridge. As you come off the bridge you want to head right in front of Southwark Cathedral which joins you to the start of the southbank.
Not sure of your timings but Borough Market is just behind the cathedral if you wanted lunch (again check opening days/times – it does get very busy). There is also another fab but small museum called The Old Operating Theatre just by the market, def check opening times/days its up a few flights of stairs. It has a great kids trail, loads of herbs/potions to small, old bottles, instruments plus the operating theatre but I guess it depends on your kids interests. We got in half price I think with NT or EH membership.
Anyway as you walk along the southbank (just keep next to the river!) you will pass the Golden Hinde (they do pirate type tours which are great but you need to book in advance I think, they are all in character – we used our tesco vouchers to do this) the clink museum, the globe and then you'll find the tate modern.
Afterwards I would continue to walk along the southbank, past the millennium bridge, oxo tower then you have the London eye, aquarium, shrek experience & the dungeons…not forgetting that on the opposite side of the river you will have Big Ben & the houses of parliament etc. It is quite a long walk but there is always lots going on down there and lots to see (and tick off!)
Loads of places to eat along here too. If you walk through the small park next to the London eye, you will come out almost opposite Waterloo where you can pick up the northern line again to take you back to Kings Cross.
You could of course always pick up a boat if not, I am sure they go by Westminster bridge on the HofP side. That is soemthing they haven't done yet.
Do you want any more suggestions for the Saturday?. We actually saw some Chelsea Pensioners (one of the things in the ISpy book) when we went to see Matilda, they were sitting in the row behind us!