Hi, We put in our built in about 20+ years ago, We go thru periods of loving / hating it. When the kids were young and used it a lot - it was great, but then they get to an age where they don't use it much and full seasons go by without anyone even using it, now my GS (4) is living with us and I'm loving the pool again, he is in it constantly during the summer.
Couple of things to remember about installing a built in- whatever you think it will cost DOUBLE it, because there is so much unexpected stuff that goes with the installation, plus now you have landscaping costs, cement/decking/paver costs, unexpected construction / permitting costs, possibily a new fence etc.
Upkeep is $$, nothing like an above ground, everything that goes wrong with a built in is $$, so first few years when everything is BRAND new will be fine, but down the line expect $ for repairs/upgrades.
Don't cheap it up, if your going to do it, go for what you really want- I insisted on a heater when we installed the pool and have never been sorry, what good is having a beautiful pool when no-one uses it because it's FREEZING.
& Get the slide- Kids will love it.
Invest in LOTS of towels, because you will officially be the "Kool-aid" house, every kid and their parents will be at your house, so anticipate more food & LOTS OF LAUNDRY!
Love my pool, but remember an built in, can't be taken down when your kids outgrow it, your stuck with it long after the kids are grown.
Good luck!!