Nitrogen is a quick leecher from the soil as opposed to P & K so your plot may be ok this year.

I did the same thing 4 or 5 years ago, also with mushroom manure. I dug some into the entire garden and then dug a couple spadefuls into the hole when I planted the tomatoes. They were beefsteaks and yellow pear tomatoes, all indeterminates. They grew 14 foot tall, but they weren't late and I got what I perceived as the normal amount of tomato production from the plants. But the following year the plants grew normally. I think you'll be fine this year and it's my opinion that digging in straw won't be a problem. You should consider your PH level particularly if you have acid soil.