"is good" is fairly easy, some form of bŏnum with the verb of being, but I'm having more trouble with the word for "fun".
Part I: "Fun"
Lūdus was my first thought because it refers to play in the broadest sense, including play in the sense of acting, games, diversions, jokes, jests, and sports. But for that very reason, it may be over-broad in the sense that a play can be a drama, and sports can be serious.
So I spread my net wider, and looked at iocor, but I find it too limited, referring only to jokes and jests.
Moving into verb forms, oblecto, fruor, and gaudĕo, all seem closer to fun, connoting enjoyment and delight, but these are more obscure that ludus, and would render the Latin less accessible to those with an interest, but only basic vocabulary. Thus there is an tension between precision and comprehensibility.
Part II: Dr. Seuss
I'd also be very interested in peoples' thoughts on a Latinization of Dr. Seuss.
Medicus seems to physiological, connoting a surgeon, which I don't believe was Seuss' intent. I suspect the type of doctor Seuss' was whimsically indicating would be closer to a rhetor, but I'm unaware of an abbreviation.
The doctor part is not essential, and could be dropped, but a solid Latinization of Seuss is critical.
Any thoughts, perspectives are welcome, as well as proposed renderings as I don't have many excuses to exercise my Latin, which is limited in any case.