I think overcarbonation is pretty much a guarantee. Bottle bombs will depend on the quality of your bottles, but I think you run a real risk.
Here's my quick, back-of-the-envelope calculation:
A) 5 oz per gallon of priming sugar generally gets you to the upper end of the preferred carbonation range. The exact amount depends on your fermentation temps, but my guesstimate is 2.8 volumes of CO2 from the priming sugar alone.
B) A conservative guesstimate for the OG of your apple juice is 1.040
C) Divide 40 by 20 (5 gallons = 19L, plus 1L of juice), means you're increasing your gravity by about 2 points
D) Each point equals roughly 0.5 volumes of CO2. This puts you in the ballpark of 3.8 volumes of CO2. Unless you're using belgian or hefe bottles, this is definitely in the "risk of bottle bombs" territory.
Check your carbonation levels frequently. As soon as they hit the carbonation levels you want, get your bottles in cold storage. Continue to monitor them frequently, and as soon as they start to show signs of overcarbonation drink them as soon as you can.