Those are good sizes, about the best you'll find in a metric 18" tire (OK, that does look self-contradicting). The width 90/90/18 is in mm so a 90mm is very close to a 3.5" "inch" tire. The 110 is wider than stock at about 4.3" but the 110/80/18 height ratio means a lower profile and it will fit OK. Choice is reducing every year for 18" tires.
These will be "tubeless" tires so getting the bead over your tube rims will be more of a chore than with old tube tires, but they will go on. Use some lube - soapy water works well - and inflate them then check that the bead line is equally spaced from the rim all the way around. If not, try overinflating them to the "max" psi rating on the sidewall, if that doesn't do it you have to pop the bead off and try reseating it. The bike will pogo a bit if the bead sits offcentre..
