I got a crossbow for my kids to use when they became legal here in IN. I have used it as well and have taken 1 deer with it. Its a nice archery tool for when you don't want to invest the money or time into more traditional bow hunting equipment. I did it to avoid a bow for me, a bow for my bow, and a bow for whoever else. Crossbow is more of a one size fits most typye of tool, much like a firearm - a compound is more tailor fitted to the individual.
It's a different animal - You muscle memory thinks gun, but it isn't. You pullthetrigger andexpect recoiland a boom. You get recoil of a BB-gun and a thump sound (not what your body is expecting). If you are used to watching the magical flight of your arrow - that is pretty much gone as well. When using a scope at 30 yards in most cases by the time you look up the bolt/arrow is there all ready. They are typically heavier, and louder than a compound. Mine is comparable to a 22 crack. They are not very balanced either - very front heavy. The multiple dimensions vs a gun or bow makes them somewhat awkward at first as well. I have not seen any increase in hunting range myself - at least not without considerable practice. I still limit myself to 30 yards. You can not use a traditional archery target -the crossbow will blow right thru most of them and tear up the bolts/arrows (bag or 3D type). Also on lower end models the trigger typically sucks! More like one of a shotgun than a rifle.
I bought a Barrnet Quad 400 (I think) as a kit (bow, bolts, quiver, practice points and 4x scope) from BP for right at $500 - scope was crap (literally fell apart with a month). I had issues with fliers with fixed heads, but have gotten much better results with mechanicals (I use 125 grain 2 blade rages). Yo don't havetoshoot crossbow heads, but you willwant to shoot a heavier head in a crossbow tha youwould traditionallyuse on a compound. I wouldn't use anythin lower than a 125gr. A crossbow bolt flight is different - there is not much rotation and the heavier head seems to pull the bolt straighter thru the air, while a true arrow uses rotation, the fletchig and the head to gain stability and address the arrow flex. Crossbow bolts are more like flinging a broomstick!
All the same they are very effective weapons on deer as long as you know your limitatons. They take some getting used to, require some,but not alot of practice t become proficient with at normal archery ranges and just like anything else you can spend alot of money on one. I shot a $1,000 one and it was a totally different weapon. Smooth trigger, much quieter, lighter and more balanced. I couldn't justify $1,000 on something I wasn't sure would get much use.
It ruins the surprize but take yor dad to a shop and have him shoot some - he may not like it, he may be like a kid ina candy store! The experiance may be the best gift of all. Crossbows are pick-up and shoot,so most archery shops will have several you can "test drive". Good luck.
P.S. - I have no regrets buying mine, but it wasn't a game changer for me personally either. Giventhe choice I prefer my compound, but if I have a hard time finding the time to practice - I can always grab the crossbow and head out and be confident.