as the title says im looking to make vampire cows for a one shot for my group. i am not experienced with making home brewed monsters or balancing encounters but im aiming for it to be a medium to easy encounter for 2-3 lvl 4or possibly 5 players with few magic items. and i would like them to not die (they are a fan of challenge though so its best not to be steam rolled). 

so the questions i mainly have is that would i use the cows stat block and add all the vampire spawns weaknesses and traits; or perhaps the vampire spawns stat block but add a gore instead of the claw? or am i not thinking about this right?  i assume that no matter what the cr will be that of a vampire spawn perhaps even higher now with the added gore?

sense it cant grapple i was thinking of changing it to strictly requiring the target to be prone

any help or insight welcome thanks

Cow with the spawn traits is what I would do. You’ll have to let me know how it goes.

ill try to remember to but its for a "just in case" one shot as our dm has been having health issues recently; so we like to have some back up games in the works to allow us to keep playing despite missing members dm or otherwise. but ya ill post here if i get a chance to run it.

Thank you, I appreciate it. Vampire Cows sounds like fun. I might save that one for a Halloween game.