Unless you have a vast amount of N scale stuff, the cost of filling a basement that size with trains of any scale is substantially more. Also, as one gets older…the larger HO scale is easier to work with. Buy her some bling, it will smooth the way. 
Good luck.
One definite benefit of HO is dummy engines. I don’t believe they exist in N scale. So to have a triple-header train, you’d need to buy 3 loco’s in N, 1 plus two dummies (no motors) in HO.
CARRfan (is that California Railroad Fan? If so you’ve been living in that lunatic asylum too long); there is a topic floating around dealing with the “worst” MRR purchase one has made. I forgot about the dummy units I have tangled with over the years (in HO, of course, although I do remember a few dummy units in N-Scale way back in the heady days - I never bought any) - I never met a dummy diesel unit I didn’t grow to hate.
Welcome to the forum, but you don’t have to fool us. We are all bitten by the model railroad bug. You don’t need to blame your four year old for wanting a layout in the basement. We all know who really wants the layout, because I doubt that the ankle biter would be concerned whether it was HO or N or whatever.
For mine, the bigger the better. 1 foot = 12" is the best. From there on down it is a compromise. A garden railway would be great, 7 1/2" or 5". G would be nice. O is wonderful if you have lots of room and lots of money. I have had to compromise on HO, and it is a pretty good scale to work in.
Thomas is good for kids, and he and his friends run on “HO” track. Think you need your scale layout and the boys can have an adjoining one where they can play with robust trains that will withstand their activity. Your wife will be happy to see you at home with the family engrossed in a great hobby.
Go for S or O, you have enough room. N scale is actually your most expensive option because you’ll wind up buying a lot more track, trains, etc to fill the space. I have been in S for several years and really like the size.
Enjoy
Paul
Wait 'til Christmas is coming and the go H0, H0, H0.
I’d say go with HO. Not so much because I’m in it myself but because 4 and 8 years old just doesn’t sound mature enough for N scale between all the tiny parts and stuff I can just picture them getting roughed up and taking a major beating. I know even at my most cautious I was like the gorilla in them suitcase commercials on my toys when I was 4. You can always sell all the old stuff on eBay and some hobby shops do a consignment deal or trades.
I would say HO scale I have a 11x11 room and I wont do N scale because the product and the maintence as said above. youll love the details in HO over N.
Well, I have been going through my fleet “de-powering” lots of units. I realized how stuipid it was to have multiple ABBA sets of all powered units when a powered AB alone could pull anything I could throw at it. All that does is demand more power blocks, heavier wiring, more decoders, more programming, more time, basically more expense for zero benefit.
I have to disagree with this. I found N-scale to be quite rugged. For the size of a child’s hands, N-scale is actually much easier for them to deal with. Think how monsterous those HO box cars cars are… Basically a two handed operation.
Dan,
I’m happy with my HO layout.I just came back from the york meet with about 150 assorted freight railcars and a few engines which I spent average about $1.00 or less per car $5.00 or less per engine. All in nice condition except for a handfull that i’m removing the trucks to make offices & storage on the set. HO does have price advantages at times. Mike
Having five grand children, a word to the wise-HO and N are not durable enough for that age group-go with O. They are more resilient to accidental oops aka breaking off detail parts-crashes-derailments-N scale is not real user freindly to younger ones. I have a o scale and N scale layout-the O is currently in storage and the O scale was the hands down winner as it has more operating accessories as well. Keep it simple. They can always graduate to smaller scales.
As you have seen, you’ll get advocates of just about every scale available especially with that kind of space. Although, I don’t remember seeing anyone mention the virtues of TT scale yet.
Before doing anything else, get yourself a copy of Armstrong’s book “Track Planning for Realistic Operations.” It may be the most referenced book on this forum. Then, before settling on a scale, develop the list of things you feel you must have in the layout, and then things you want to have, and then things that would be nice. Part of this has to be things like the minimum and normal aisleway width you are going to use, preference for era, equipment size, size of the railroad operations (long trains, short trains, a lot of switching, etc). Call that the “givens and druthers.”
Then look at the space and figure out where the obstacles are. Do you have a furnace, water heater, electrical panels, sump pump, exterior doors, etc. that need to be accessible? All of this will give you an available space diagram. The available space diagram is still scale independent.
The book I mentioned above will talk about designing using the “squares method.” I have found that invaluable in the early planning stages. The size of a square is equal to your minimum mainline radius plus twice your track centers (a 36" radius with 2" track centers will give you 40" squares). Dividing your available space diagram into squares will tell you what will fit and how large of a minimum radius you can adopt.
The long and short of this is that you can start to nail down a layout shape, without regard to scale, by knowing these things. Once that is done, you’ll begin to figure out what will fit in what scale(s) and what won’t. The choice of scale may still boil down to personal preference, but at least you will have considered most everything that might bite you later on.
I switched to N about 5 years ago, and will stay with it almost regardless of the size of my next available space
HO HO HO…