Couple of things about parking at Watford: There are two or three stations there. You want the one on 'Cassiobury park ave'. It's on the metropolitan line, which goes direct to Wembley. We arrived at lunch time and there was plenty of parking. It cost £2.00 for the day (pay and display). It's right next to the station so hardly any walking. The ticket cost less than a tenner (£9.80 I think) adult return. And the journey is about 25 minutes. You do drive through Watford town centre but it was no biggie following the sat-nav. Look on the 'NCP' website it tells you all the details of car parks on the metropolitan line. I thought Rayners lane looked good (multi storey), and would have tried Stanmore too. The main thing to consider is the queue for the return journey. It's huge! The police managed it really well so it did move quickly. But I would think a 4 year old would find it a bit scary. 2014 final we got a cheap hotel and I wish we'd done that this time. We went to the FA cup on Saturday, because of the extra time we got back to Hull at 2.30 am. Nightmare. UTT.
Any ideas were to park a 49 seat coach other than wembley? Getting out after Sheff Utd was a nightmare
Free coach parking, but only if you spend £20 per couple (so it's not free and you presumably need to be couples) http://www.thegreenmanhotelatwembley.co.uk/parking.htm