If you're not comfortable fighting huge field battles I wouldn't reccomend it

Mongol cavalry and archers are really powerful, they outnumber you with both quality and quantity.
I'd really recomend you getting them in bridge battles and defending in sieges.
Remember that they wont necessery come after you. If they settled in Kiev they could easily go for Poland Russia or Hungary first. At the time they meet you, they can be bled out

If you have some settlements near it could be a good idea to sell it to one of the factions I mentioned before, you could also try selling it to the pope and see what happenes
