You can walk to the Radisson, depends on how much luggage you have really and whether the weather is fine. We had 4 bags and 2 sets of skis plus hand luggage. We were in the Maldron (opposite the Radisson) and used their shuttle. Probably could have walked but couldn't be bothered because there was a howling gale and it was chucking it down.

The Radisson shuttle departs outside T1 from what I can remember.

We transferred from T5-T2 at Easter and you just follow the signs and get the bus to the other terminal. IIRC in T5 there were staff making sure you got on the bus correctly.

My kids are now 8 & 6 and due to the fact that everyone always needs the loo last minute we always end up rocking up to the gate fairly late on in boarding. When they were much smaller, I used to prefer to get there for the start of boarding so that I could get comfortable and get familiar with the bassinet etc.

You can usually gate check the stroller, in fact the US airlines are sometimes better at this than others but you should get it back at the gate at the other end.

Hope that helps