Best time to visit Alaska

[UKCraig]

I'm planning a trip to Alaska as part of a much bigger trip but I am struggling to decide when to visit. I have two options and would welcome your opinion.

Here's a rough outline of my plans:

1st/2nd May - fly from London to Tampa to visit friends
6th/7th May - leave Florida and head up, via Congaree NP, to Myrtle Beach
10th May - Nascar (Darlington NC, USA)
11th May - head over to Mooresville NC and visit Nascar raceshops
12th - 24th May - head up north visiting Shenandoah NP, Washington DC (skip NYC) and Boston. Stop at Rockport MA to visit friends then on, through Acadia NP, across the border through Montreal, Ottawa and Toronto before returning to the US and heading to Indianapolis
25th May - Indy 500 (Indianapolis IN, USA)

From here I have four weeks until my next definate 'date' - the start of my previously planned trip on 22nd June.

Initially I thought that I would do something like this:

26th May - 21st June - drive across country in the general direction of LA, taking in as many national parks as possible, then head up to San Francisco area
22nd June - Toyota/Save Mart 350 Nascar race at Sears Point
23rd June - 12th July - Slight rejig of the Yellowstone loop trip which would now hit Redwood National Park before turning north
13th July - 14th August (give or take) - another route through the north west and south west Canada. Drop car in Seattle
15th August - make way to Alaska via Alaska Marine Highway (how long does this take???)
On arrival - Trek America/Suntrek organised tour then pick up car for a few days then
Mid September - fly to Hawaii.

I am now reading that, contrary to earlier advice, August is not going to be a great month to visit as it's likely to be constantly raining (in as much as Alaska's weather is predictable!) and I am wondering if I should somehow try to shuffle things so, after Indy, I fly to Alaska before heading south through Canada and the Western US before flying out of LA or San Fran to Hawaii.

What are your thoughts? I guess it comes down to how unpredictable the Alaska weather is... will going in late May/early June offer me a greater chance of good weather? Is it worth the extra effort of rejigging everything which currently seems to work?

I would appreciate your thoughts on that, as well as any other points you see as a problem or if you have any suggestions for improvements.

Does anyone have any experience with the Alaska Maritime Highway? I've checked out the timetables but can't make head nor tail of it to be honest. Is it a huge huge trip to go all the way to Alaska on it? Is it hugely expensive as a foot passenger? Would I be totally bored by the second day? Would I be better off to fly to Alaska then spend more time there, maybe including a few ferry journeys to specific destinations in Alaska itself?

I would also appreciate any feedback ref any companies who could do me the best deal on a rental car. Will pick up in Tampa upon arrival and drop in Seattle four months later. Must be able to cross the border into Canada.