Patrick Donohoe's holding in the 1834 tythe valuation.
Note the areas are Irish, not English acres.
http://titheapplotmentbooks.nationalarchives.ie/reels/tab//004625690/004625690_00526.pdf
Same thing here, parish of Lavey, matches the feaugh of the first record.
1855 record for Patrick Donohoe's holding in Feaugh.
You can see the size, condition and rating of his house, barn and byre.
http://census.nationalarchives.ie/reels/vob/IRE_CENSUS_1821-51_007246925_00902.pdf
Feaugh is in the Loughtree Upper Barony would have been 30km away from Feugh Bishops, in the Loughtee Lower Barony/Drumlane parish.
So unless I'm mistaken, not likely to be a match.
I am not personally familiar with Cavan and its social geography, so this is precisely the sort of double checking you need to do. 
In my own family most marriages were with the "Girl next door", or at least from the same or adjacent parishes. That said, though, there were exceptions, some surprising exceptions, that I was only convinced of by DNA matches appearing. Specifically a few marriages at 30 km distance in the 1830s by modest farming families. So 30 km is not out of the question if they were two farming families that would meet at a common market town. Remember that farmers had to frequent a market.
As a check, I would look in detail at spelling variations for the townlands, which you can find on logainm.ie and townlands.ie
Very fair questions to ask, and I certainly don't want to rule out anything prematurely.
All of the Donohoe children baptism record listed their residence as being Feugh, in the Drumlane parish. They were baptized at (most likely) St Mary's Church in Staghall (and if not, St. Patrick's just a few kms away), which is also 23km away from that townland. One child's baptism record was even listed as being from Feugh Maxwell. So if they were in fact from Feaugh in Lavey, that would conflict with all their baptism records.
In a tythe valuation of 1833, the civil parish of Drumlane is returned as part of the parish of Drumgood, so have to search the latter.
Quite a few Maguires, see this search. Note in particular James in Drummullagh.
http://www.rootschat.com/links/01tln/
Good find. Also a widow Maguire in Cruny (Creeny), same townland where William was born. Possibly a grandma or aunt?
Also one James Mcguire, in Feaugh (could be same person as above? - I don't know)
http://www.rootschat.com/links/01tlo/
Also a Pat Donohoe in Feaugh:
Donoho Patt Feaugh Drumgoon Cavan 1833, which is Feugh Bishop in the writing, which lines up with the Donohoe children records I found previously.