Unless the toadstools are forming a ring, they're not related to the bald patches in your grass. The toadstools in themselves are nothing to worry about, they're just the fruiting bodies of underground mycelium, but these usually occur in autumn, sometimes spring, so its another clue that the weather is utterly appalling this year.
The cause of the bald patches is probably something else - there are many reasons for this to occur, from dog damage, scalping when mowing, right through to various diseases and infections, so hard to say why they're happening without more info.
When you say you tried to reseed, what procedure did you follow? It is necessary to rake up a fine tilth of at least an inch when reseeding - it also won't grow if you've used any lawn granular treatments within the preceding4 weeks - a gap of 6 weeks is necessary before reseeding, and about a week or two with any liquid applications.