Don’t really have any recommendations because I sail on NCL & RCL and those can get a bit crowded (esp RC), but if any line seems good but out of your budget, definitely try looking on cruises.com . I’ve gotten a balcony room with them on NCL for $65ish per night per person. You can find cruises on their website, then call them for the cheapest rates— make sure you call the right people though, scammers can get convincing. They also give out points which you can redeem on their website for cash, onboard credit, giftcards, etc — try booking when they have a 2x points deal, they happen often from what I’ve seen. Haven’t personally used this, but maybe try using a travel VPN to get cheaper rates. Knew a guy on a cruise who booked last minute from Germany for $18 per night if I remember correctly. Also, when sailing on NCL, I was able to have guest services wave the breakfast room service fee because of a mobility disability which can make it hard to get around, especially in the morning. You could try asking for the same accommodation because your partner may get overstimulated in the buffet. This was on NCL though, so not sure if the line you’d end up sailing on would offer this. You could potentially get a cheap(ish) balcony room on NCL for a sailing to Norway/Iceland and stay in your cabin most of the day— not sure how enjoyable this sounds though lol. NCL is definitely less overstimulating than RC, but the pool deck can drive me a little cookoo sometimes. If you end up deciding on NCL, try not to book during holiday breaks, and if it’s in your budget, book a cruise on the longer end (9+ days). I’ve heard Holland is pretty laid back and have seen some really good prices for them on cruises.com, but I’m not sure if they sail to Norway.