Wanted

I assume you mean a Scamp 16 (Options are 13, 16 and 19)
I hope you have seen some of them in person. Scamp layout 4 could work but even the 16 is none too big for 2 adults and 2 children.

Don't wait on seller to come to you.. the market is way to hot now for sellers to spend time looking for buyers (unless you get lucky). Places to look:

https://www.fiberglass-rv-4sale.com/scamp-trailers-for-sale
https://www.fiberglassclassifieds.com/
https://scampowners.com/forums/member-trailers-sale
https://www.facebook.com/marketplace
https://www.facebook.com/groups/731164040326972/
https://www.facebook.com/groups/814001036000426/
https://www.searchtempest.com/ (also see https://www.craigslist.org/about/scams)
https://www.ebay.com/b/Auto-Parts-and-Vehicles/6000/bn_1865334 (use "other tab")
https://www.rvtrader.com/find-rvs-for-sale
Ask Scamp (Evelands) to be on a standby list.

Scamp is 16’, not 17’, and it has a narrower main bed (45”” vs. 54”) than the Casita and Escape. They’re the same beds as our 13’ Scamp. We made them work for four by doing a bit of creative rearranging. My wife shared the main bed with one of the kids, sleeping head-to-toe. I split the front bunks with the other. Tongue weight on the Casita will exceed your 350# rating. Base empty tongue weight is 365# and typical loaded tongue weights are around 425#. Casita recommends a 5000/500# minimum rating. Escape is between the two in weight and within your ratings, but more expensive. You will probably want to use a WDH. If you’re shopping used, Scamps are most common and Escapes (with the front bunk option) the rarest. Oddly enough, it’s easier to find a 13’er with beds for four than a larger unit. But you can’t have a bathroom.